Here my code with a collapsible navbar. The toggler button opens but not closes the menu:
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.1/font/bootstrap-icons.css" integrity="sha384-4LISF5TTJX/fLmGSxO53rV4miRxdg84mZsxmO8Rx5jGtp/LbrixFETvWa5a6sESd" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.7.1.min.js" integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo=" crossorigin="anonymous"></script>
<script src="https://code.jquery.com/ui/1.14.0/jquery-ui.min.js" integrity="sha256-Fb0zP4jE3JHqu+IBB9YktLcSjI1Zc6J2b6gTjB0LpoM=" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.min.js" integrity="sha384-BBtl+eGJRgqQAUMxJ7pMwbEyER4l1g+O15P+16Ep7Q9Q+zqX6gSbd85u4mG4QzX+" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/2.9.2/umd/popper.min.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/select2-bootstrap-5-theme@1.3.0/dist/select2-bootstrap-5-theme.min.css" />
<nav class="navbar navbar-expand-lg navbar-dark" style="background-color: #134d8c;">
<div class="container-fluid">
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav me-auto mb-2 mb-lg-0">
<li class="nav-item">
<a href="/www" class="nav-link <?php echo ($page == 'home') ? 'active' : '' ?>">
<i class="fs-5 bi-house"></i> <span class="ms-1 me-2 d-none d-sm-inline">Home</span>
</a>
</li>
<li class="nav-item">
<a href="parametri.php" class="nav-link <?php echo ($page == 'parametri') ? 'active' : '' ?>">
<i class="fs-5 bi-gear"></i> <span class="ms-1 me-2 d-none d-sm-inline">Parametri</span>
</a>
</li>
<li class="nav-item">
<a href="anagrafiche.php?nav=anagrafica_alunni" class="nav-link <?php echo ($page == 'anagrafica_alunni') ? 'active' : '' ?>">
<i class="fs-5 bi-backpack2"></i> <span class="ms-1 me-2 d-none d-sm-inline">Anagrafica alunni</span>
</a>
</li>
<li class="nav-item">
<a href="anagrafiche.php?nav=anagrafica_famiglie" class="nav-link <?php echo ($page == 'anagrafica_famiglie') ? 'active' : '' ?>">
<i class="fs-5 bi-people"></i> <span class="ms-1 me-2 d-none d-sm-inline">Anagrafica famiglie</span>
</a>
</li>
<li class="nav-item">
<a href="bonus.php" class="nav-link <?php echo ($page == 'bonus') ? 'active' : '' ?>">
<i class="fs-5 bi-trophy"></i> <span class="ms-1 me-2 d-none d-sm-inline">Bonus</span>
</a>
</li>
<li class="nav-item">
<a href="turni_pulizie.php" class="nav-link <?php echo ($page == 'turni_pulizie') ? 'active' : '' ?>">
<i class="fs-5 bi-trash"></i> <span class="ms-1 me-2 d-none d-sm-inline">Turni pulizie</span>
</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
<i class="fs-5 bi-cookie"></i> Turni cucina
</a>
<ul class="dropdown-menu" aria-labelledby="navbarDropdown">
<li><a href="turni_cucina.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina') ? 'active' : '' ?>">Calendario</a></li>
<li><a href="turni_cucina_famiglie.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_famiglie') ? 'active' : '' ?>">Famiglie</a></li>
<li><a href="turni_fissi_cucina.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_fissi_cucina') ? 'active' : '' ?>">Fissi</a></li>
<li><a href="turni_cucina_scambi.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_scambi') ? 'active' : '' ?>">Scambi</a></li>
<li><a href="turni_cucina_pagamenti.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_pagamenti') ? 'active' : '' ?>">Pagamenti</a></li>
</ul>
</li>
</ul>
</div>
</div>
</nav>I found this similar question, but my code seems already as the answer suggests (include jquery before bootstrap). Why it works in one way only?
By removing bootstrap.min.js, it works properly.
It's conflicting with the bootstrap.bundle.min.js.
If you specify bootstrap.bundle.min.js you don't need to include the bootstrap.min.js, it's redundant.
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.1/font/bootstrap-icons.css" integrity="sha384-4LISF5TTJX/fLmGSxO53rV4miRxdg84mZsxmO8Rx5jGtp/LbrixFETvWa5a6sESd" crossorigin="anonymous">
<script src="https://code.jquery.com/jquery-3.7.1.min.js" integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo=" crossorigin="anonymous"></script>
<script src="https://code.jquery.com/ui/1.14.0/jquery-ui.min.js" integrity="sha256-Fb0zP4jE3JHqu+IBB9YktLcSjI1Zc6J2b6gTjB0LpoM=" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/select2-bootstrap-5-theme@1.3.0/dist/select2-bootstrap-5-theme.min.css" />
<nav class="navbar navbar-expand-lg navbar-dark" style="background-color: #134d8c;">
<div class="container-fluid">
<button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav me-auto mb-2 mb-lg-0">
<li class="nav-item">
<a href="/www" class="nav-link <?php echo ($page == 'home') ? 'active' : '' ?>">
<i class="fs-5 bi-house"></i> <span class="ms-1 me-2 d-none d-sm-inline">Home</span>
</a>
</li>
<li class="nav-item">
<a href="parametri.php" class="nav-link <?php echo ($page == 'parametri') ? 'active' : '' ?>">
<i class="fs-5 bi-gear"></i> <span class="ms-1 me-2 d-none d-sm-inline">Parametri</span>
</a>
</li>
<li class="nav-item">
<a href="anagrafiche.php?nav=anagrafica_alunni" class="nav-link <?php echo ($page == 'anagrafica_alunni') ? 'active' : '' ?>">
<i class="fs-5 bi-backpack2"></i> <span class="ms-1 me-2 d-none d-sm-inline">Anagrafica alunni</span>
</a>
</li>
<li class="nav-item">
<a href="anagrafiche.php?nav=anagrafica_famiglie" class="nav-link <?php echo ($page == 'anagrafica_famiglie') ? 'active' : '' ?>">
<i class="fs-5 bi-people"></i> <span class="ms-1 me-2 d-none d-sm-inline">Anagrafica famiglie</span>
</a>
</li>
<li class="nav-item">
<a href="bonus.php" class="nav-link <?php echo ($page == 'bonus') ? 'active' : '' ?>">
<i class="fs-5 bi-trophy"></i> <span class="ms-1 me-2 d-none d-sm-inline">Bonus</span>
</a>
</li>
<li class="nav-item">
<a href="turni_pulizie.php" class="nav-link <?php echo ($page == 'turni_pulizie') ? 'active' : '' ?>">
<i class="fs-5 bi-trash"></i> <span class="ms-1 me-2 d-none d-sm-inline">Turni pulizie</span>
</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
<i class="fs-5 bi-cookie"></i> Turni cucina
</a>
<ul class="dropdown-menu" aria-labelledby="navbarDropdown">
<li><a href="turni_cucina.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina') ? 'active' : '' ?>">Calendario</a></li>
<li><a href="turni_cucina_famiglie.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_famiglie') ? 'active' : '' ?>">Famiglie</a></li>
<li><a href="turni_fissi_cucina.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_fissi_cucina') ? 'active' : '' ?>">Fissi</a></li>
<li><a href="turni_cucina_scambi.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_scambi') ? 'active' : '' ?>">Scambi</a></li>
<li><a href="turni_cucina_pagamenti.php" class="ms-1 me-2 nav-link <?php echo ($page == 'turni_cucina_pagamenti') ? 'active' : '' ?>">Pagamenti</a></li>
</ul>
</li>
</ul>
</div>
</div>
</nav>Also: you don't need to link the popper.min.js, it's included in the bootstrap.bundle.min.js!
For further reading: https://getbootstrap.com/docs/4.4/getting-started/contents/#js-files