If a web browser starts loading the web page but it never finishes loading it, look for the resources being loaded and the debug errors in F12 Developer Tools.
If the page has an iframe, try testing the page after removing the iframe. If it works without the iframe, then look for further leads to narrow the issue down.
SameSite cookie prevents cross-site request forgery (CSRF) attacks by restricting the usage of third-party resources in web applications. Resource examples are the URLs in GET, POST, link, iframe, Ajax, image etc. If a URL is different than the actual web application’s URL, it means that it’s a third-party resource.
Developers use SameSite cookie attribute to prevent CSRF (Cross-site Request Forgery) attacks. This attribute instructs browsers not to send cookies along with cross-site requests (Reference).
I needed to turn of SameSite cookie attribute for Safari as part of a fix to the issue mentioned here. A simple solution is below.