I restarted and all is well. Thanks.

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems.

So I'm continuing to have this problem intermittently. I'm using Safari right now. It seems like it only happens in the morning, later in the day I can access the site with no problem. It appears I'm the only one reporting this issue, so I assume that it's a problem between my iMac and Firefox. Any ideas? Thanks.

Hi,

I think you can fix this by using firefox in safe mode.

Open firefox and click on open menu. Then click Help. From there select Restart with add-ons Disabled. Then click Restart. Finally select Safe Mode in start.

In some cases, incompatible add-ons may cause the firefox not to open. Also, firefox can be slow because of this reason.

To get rid of it,

Open firefox and select open menu. Click Add-ons. Select Extensions or Themes you want to remove. Finally click the Remove button and select Restart now.

Thank you!!

Refreshing Firefox {web link} is a LAST RESORT ! !

Refreshing Firefox -- easily fix most problems

If you're having problems with Firefox, refreshing it can help. The refresh feature fixes many issues by restoring Firefox to its factory default state while saving your essential information like bookmarks and open tabs. Everything else, like user settings and add-ons, are removed.

Note: Refresh saves your old profile to the desktop in a folder called Old Firefox.

I "refreshed" Firefox and it worked OK for a day. I began having problems again yesterday, but now I'm getting an error message "Close Firefox. There is another session of Firefox open" - not an exact quote - when it appears it is not open. I'm using Safari to communicate now. The only way I can get Firefox to start again is to restart my iMac. I recently upgraded to Catalina. Could that be a problem? Thanks.

I "refreshed" Firefox and it worked OK for a day

What did you do with the browser? Add-ons, settings . . . .

All I can think of is setting Yahoo.com for my home page. I was prompted to reenter my user ID and password in some sites. That's about it.

Try refreshing Firefox again. But don't change anything.