This has been going on since at least when Chase changed over to Express Web Connect + and probably longer, as reported by many people. My past theory was that Quicken detected some kind of error and just treated it wrong and reported the account closed (CC-800, and closed icon on the account in the account bar).
First off, Quicken should never mark an account closed without the user's approval.
But past that this just happened to me again today, and I took a close look at the cloud sync log. I had updated successfully last night, and so there wasn't any new transactions, which might be part of the problem of Quicken not behaving correctly. But in any case, all the balances for my banking accounts including the two credit card accounts that it marked as closed were reported correctly with no errors. But still Quicken reported the two credit cards accounts closed, but not the checking account, which was in the same response for the balances.
I have used "Report a problem" to send the logs to the Quicken developers. I hope that they can get this resolved but given how many people have already reported this my confidence in that is pretty low.
But at least now I will revise my theory that this is a falsely reported error.