Hi Maybelle, 

Thanks again for your input, but this was not likely caused by a cache or cookies issue: all of my other accounts were able to toggle. This is most likely a bug in QBSE which prevents an account from being altered if QBSE cannot complete a "handshake" with the institution's API. I surmise this will happen if the institution closes an account while QBSE is still configured to sync with it. The sync fails and QBSE puts the account in an errored state until the user (me) reestablishes the connection, which can't actually be done because the account is closed. The effectively "locks" the account in such a manner that QBSE can never recover.

My bank account is now completely logged out (i.e. sync is disabled) and the only option QBSE offers is a complete deletion of the account which is not an appropriate solution.

Please escalate this as a possible (probable) defect to your product managers.

Thank you!