Reason: The #1 reason why this is happening is because your browser is thinking that Dynmap is an unsafe site since it is unsecure, so it will block you from viewing the dynmap from Luminant's website.

How to fix: When you are viewing the Dynmap in a separate tab (not the one on the website) click the thing at the top left that says "Not-Secure" or sometimes it can just show a caution symbol. Then go to "site settings". This will take you where you can set up the permissions of the website. Go ahead and click on "Privacy and Security" then scroll down on the page until you find something called "Insecure Content". To the right of this option, go ahead and set it to "Allow". This should tell your web browser that dynmap is safe to be on, and don't block it.

Reason: For some reason, certain browsers will not support the dynmap preview and will not, despite your attempts, work properly. This likely causes the dynmap to keep continuously loading.

How to Fix: I found that using Opera GX works really well with this type of stuff, as well as using Google Chrome , which I believe is another supported browser.