see this answer:

• https://support.mozilla.org/en-US/questions/1229670#answer-1143325

This issue can be caused by corrupted cookies or cookies that are blocked.

• check the permissions for the domain in the currently selected tab in "Tools -> Page Info -> Permissions"
• https://support.mozilla.org/en-US/kb/fix-login-issues-on-websites-require-passwords

Clear the Cache and remove the Cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Remove the Cookies" from websites that cause problems:

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Manage Data

"Clear the Cache":

• Options/Preferences -> Privacy & Security
  Cookies and Site Data -> Clear Data -> Cached Web Content: Clear

If clearing cookies didn't help then It is possible that the cookies.sqlite file in the Firefox profile folder that stores the cookies got corrupted.

• rename/remove cookies.sqlite (cookies.sqlite.old) and if present delete cookies.sqlite-shm and cookies.sqlite-wal in the Firefox profile folder with Firefox closed in case cookies.sqlite got corrupted.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Thank you, Cor-el, for your reply.

The fix is out there, and somebody knows what it is.

Troubleshooting the Old Fashion Way Troubleshooting time this session 6.5 hours

Problem: Some websites' downloads would not download, and with no error, it just didn't Some websites would not complete login, no error, it just wouldn't, example: https://www.usbank.com

Spent a lot of time getting nowhere using these steps. http://kb.mozillazine.org/Unable_to_save_or_download_files https://support.mozilla.org/en-US/kb/cant-download-or-save-files#w_delete-corrupt-plist-file

With every add on disabled, success.

Remember Conflict Catcher, the utility that streamlined the process of identifying bad inits and CDEVs that loaded upon bootup?

Had to do what Conflict Catcher does, manually, to figure out which add ons were causing the above 2 problems.

Sequence used. Cleared every option under Clear History, and rebooted Firefox between each test. Caveat, and major headache. Results of each test are not always the same; sometimes success, sometimes failure. All I could do is come up with a fair probability that I found the cause.

Again, the answer is out there, I just don't have it.

Getting started:

Add ons. 1Password Extension Adblock Plus Bookmacster Sync DNS Over HTTPS Download Statusbar DuckDuckGo Privacy Essentials Evernote Web Clipper Fakespot Ghostery Greasemonkey Privacy Badger Zoom Page WE Cookie AutoDelete Lechblock NG Popup Blocker Strict

Definitions: Test = Testing the 2 situations while some addons are enabled, some disabled. Success = Download that wouldn't download, downloaded. AND login that wouldnt login, Logged in as it should Failure = One or more of the 2 problems occurred. Mixed = Success sometimes, Failure sometimes, upon the same test.

Testing half at a time, alphabetically, Results were MIXED, hence useless.

Next I decided to test only those addons that pertain to privacy, by adding them one at a time, clearing history and rebooting FF, then testing the banking website to see if it would login.

Here's the results, adding them one by one and testing All Disabled - Success Added Adblock plus - Success Added Duck Duck Go privacy essentials - Success Added Ghostery - Success Added Privacy Badger - Success Added Privacy Possum - FAILURE Disabled Privacy Possum and continued, Added Cookie Autodelete - Success Added Leechblock NG - Success Added Popup Blocker Strict - Success

Conclusion: None, not possible, If I repeated the above test many times more, results would likely be eclectic. I would have to spend hours or days repeating these test over and over until I could get a reasonable probability as to which add on should be deleted. By itself, Privacy Possum works fine, to find out which add on or add on's aren't playing nice with privacy possum, will take more time than I have.

Why am I doing all this? It's because Firefox happens to be the best, and I am fed up with going to Safari just to login to stubborn websites.

Again, the real solution is out there! I just haven't the time to ferret it out.

Recommendation: A conflict-catcher type of application should be developed to automate the process of identifying add-on's that don't play nice with each other.

You need to contact the developer of Privacy Possum for support if there are problems with his extension.

• https://addons.mozilla.org/en-US/firefox/addon/privacy-possum/

Hi Cor-el, thanks for the link. I don't want to inappropriately point the finger at Privacy Possum, which happens to be an excellent add-on, unless I can substantiate my inference that Possum may have a fault.

Perhaps another add-on is interfering with Possum inappropriately, I dunno. I would have to do a lot more "conflict catcher style" troubleshooting to narrow it down.

And too, with each Firefox update, all bets are off and I would start from the beginning. The login problem with citibank began before I even knew about possum. FF upgrades came along, time passed, and without me changing anything, citibank logins are ok and USbank logins quit working until I did all the troubleshooting I described.

I don't want to accuse the Possum developer of anything, given that it may be another process or addon or who knows what, causes the presence of Possum to inhibit a login. It could be Firefox itself that, in the presence of Possum, inhibits logins and downloads, all this is way above my pay grade, and far smarter mac users will surely know the answer.

I'll provide the Possum developer with this link with the caveat that my findings may become baseless pure speculation. It's the combination of using Possum and other things that causes some logins to fail; for me to find that combination will take an enormous amount of hours. It may be a combination of several things causing the problem. I use System Sierra, and that may have something to do with it, or it could be lots of websites have code rot, contributing to the problem.