Thank you for reaching out to the Community regarding your issue, though I am sorry to hear that you are experiencing this.
With the amount of time you've been experiencing issues it's difficult to say what exactly is causing the issue you're having, as such we would recommend contacting Quicken Support directly for the best assistance. They'll be able to collect logs if needed to diagnose what's causing you to not be able to connect to the FI's you've listed. I will leave our hours down below so you can find a time that works best for you.
Click here to review Quicken Support's hours of operation.Thanks, Quicken Francisco
Are you Syncing to Mobile/Web? AND do you use the Mobile app on your smartphone or the Quicken on the Web feature?
If you answer "no" to both, turn Sync off completely. You don't need it. The Sync process should only be used in conjunction with the Quicken app for Smartphones or the Quicken on the Web browser app. It cannot be used as a replacement for backing up and restoring your Quicken data file.
If "yes", try to Reset Sync so that the current cloud sync file is replaced with a fresh complete copy Do note that a full Sync process may take many minutes to complete.
Log out of your mobile app, then do this on your desktop / laptop:
How to reset Sync to Cloud
How to turn off Sync to Cloud for the current data file