Make sure you are not blocking content.

Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}acking-protection-firefox-desktop

I tried starting in safe mode and that didn't work. I was afraid to delete the Twitter cookies because I thought it would affect my other browsers that were able to access Twitter. I finally got up the nerve to delete the Twitter cookies in Firefox and that resolved the issue. Thank you for your help.

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution.

Thank you for contacting Mozilla Support.

I cleared the cache and deleted the Twitter cookies and my problem was resolved. I was able to log into Twitter again.

Thank you for letting us know.

I had a similar issue myself - from what I have heard there was a problem that Twitter had (not Firefox) yesterday afternoon.

I'm glad I wasn't alone. I'm not surprised that it was Twitter!!