In chrome website rendering in iframe with different domain is unable to set and get cookies

Website a.com is rendering b.com in iframe. When running website b.com alone, everything is working fine. But when running a.com, website b.com is unable to set or get cookies.

• a.com has no part in set or get cookies. b.com is setting or getting cookies
• Cookies are set/get using https://cdn.jsdelivr.net/npm/js-cookie@2/src/js.cookie.min.js
• Cookies are set with samesite as none and secure as true.

Cookies.set(Key,Value,{sameSite:'None',secure:true,expires:30,domain:'b.com'})

• When changing same-site option in chrome://flags from default to disable, everything is working as it should.

Iframe child cookies cannot be set in parent and vice versa. It is restricted due to security reason. The best possible way is using postmessage from parent widow.getElementById("iframeId").contentWindow.postMessage("your message","*");

Child listen to that message

    const allowedOrigins = new Set();
    allowedOrigins.add('localhost:3000');
    await window.addEventListener("message", (event) => {
    if(event.origin) {
    const originUrl = new URL(event.origin);
    const originHost = originUrl.host;
    if(!allowedOrigins.has(originHost)) {
        return;
    } else {
        //do your thing
      }
    }```