Disable products purchases that don't have specific tags in WooCommerce

/*
 * Disable buying products from specific category and tag
 *
 * @author Misha Rudrastyh
 * @url https://rudrastyh.com/woocommerce/make-products-non-purchasable.html#specific-categories
 */
add_filter( 'woocommerce_is_purchasable', 'misha_catalog_mode_on_for_category', 10, 2 );
function misha_catalog_mode_on_for_category( $is_purchasable, $product ) {
    
    // Second – check product tags
    if( has_term( 'available', 'product_tag', $product->get_id() ) ) {
        $is_purchasable = true;
    }
    
    return $is_purchasable;
}

I want to enable add to cart button only for the products with tag called available and make add to cart button hidden on rest of the products on WooCommerce.

I have tried to enable add to cart button on the selected products with tag available but it doesn't disable other products.

To make all products unavailable on WooCommerce except those with the tag available, you need to make is purchasable false before you make it true only if your condition is met.

/*
 * Disable buying products from specific category and tag
 *
 * @author Misha Rudrastyh
 * @url https://rudrastyh.com/woocommerce/make-products-non-purchasable.html#specific-categories
 */
add_filter( 'woocommerce_is_purchasable', 'misha_catalog_mode_on_for_category', 10, 2 );
function misha_catalog_mode_on_for_category( $is_purchasable, $product ) {
    $is_purchasable = false;
    // Second – check product tags
    if( has_term( 'available', 'product_tag', $product->get_id() ) ) {
        $is_purchasable = true;
    }
    
    return $is_purchasable;
}