Boot the computer in Windows Safe Mode with network support to see if that has effect.

• https://www.bleepingcomputer.com/tuto.../how-to-start-windows-in-safe-mode/
• https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/

You can check the Web Console (Tools -> Web Developer) for messages about blocked content and about the presence of mixed or unsafe content.

• https://firefox-source-docs.mozilla.org/devtools-user/web_console/

You can check the Network Monitor to see if content is blocked or otherwise fails to load.

• https://firefox-source-docs.mozilla.org/devtools-user/network_monitor/

If necessary use "Ctrl+F5" or "Ctrl+Shift+R" (Mac: Command+Shift+R) to reload the page and bypass the cache to generate a fresh log.

Try changing DNS over HTTPS (DoH) to "Off" or "Max Protection" and in Connection Settings change "Use system proxy settings" to "No proxy".

I believe it was a Kaspersky Internet Security issue. With the blockers and tracking turned off as I noted above, I went into Kaspersky and turned 'on' then back 'off' (or 'off' then 'on') several security items and rechecked the sites. They work fine now. I think it was just the banner setting in Kaspersky that was changed (not sure how) that lead to the issue. I have re-enabled some blockers and re-enabled enhanced tracking and the sites are still workable. I think this issue can be closed. It was not a Firefox issue. I appreciate the responses received from several users and apologize for wasting their time.

No problem. Mark this issue as resolved to remove it from our list and have a nice day.