Hmm, same Pinterest account login in all browsers? Should see the same site content in all browsers.

Some things to check for:

Double-check content blockers: Firefox's Content Blocking feature and extensions that counter ads and tracking may break websites that embed third party content (meaning, from a secondary server).

(A) Do you see a shield icon toward the left end of the address bar, near the lock icon? More info on managing the Tracking Protection feature in this article: What happened to Tracking Protection?.

(B) Extensions such as Adblock Plus, Blur, Disconnect, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you may need to click the button to see what's going on and test whether you need to make an exception for this site.

Testing in Firefox's Safe Mode: In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

My wife ended up just logging out on Pinterest home page, and everything started working for her without even logging in again. There must have been a fluke in the delete cookies process that caused Pinterest not to recognize it was her account even though it displayed her correct name. It was as if the log out process acted as though she logged in. I realize that is not what happened, but it indeed was the result.

Thanks for all you effort. You certainly have a much more technical knowledge that most people, and we appreciate your effort.