This issue seemed to start with MidFirst updating their website / webapp. Trying to subsequently download transactions from MidFirst, Quicken started reporting error CC-507 - that there was an error with an account type mismatch or something similar. I have two existing accounts at MidFirst that have been in Quicken for years. I was just trying to download transactions. So I deactivated the online link and then attempted to reactivate the account. Now, get an error message that Quicken cannot communicate with MidFirst's servers.
Again, this seems like MidFirst's new app or security feature changes are the cause but I'd imagine the fix is on the Quicken side.
Any help is appreciated