I am getting a CC-501, "We are unable to update this account due to an unknown error." message every time I try to update this account. This has been happening for over a week now.
Do you have any accounts that are closed out at NFCU that are still set up for downloading in Quicken? If so, deactivate that account(s). Then try to run OSU, again.
If that doesn't apply or doesn't resolve the issue: If you have not already done so, you might want to try doing the following the next time you get this CC-501 error code:
If the issue persists, you should contact Quicken Support per this Support Article: https://www.quicken.com/support/error-when-using-online-services-cc-501/ .