Accounts are marked as DISABLED (or problematic if viewing in the API console) if we receive an authentication failure from the IMAP server when trying to authenticate a user.
If you believe credentials are correct, you can try to reset the status by making a POST request with "force_status_check=1" to the following endpoint, depending on the version of the API you use:
PLEASE NOTE: DO NOT COMBINE OTHER PARAMS WITH "force_status_check".
If this fails to reset the email account status, then you will need to obtain new credentials for the account. You can update credentials by making a POST request to the same endpoint listed above with the correct credentials.
If you want to be notified each time there is a change in account status for your users, you can add a "status_callback_url" parameter to a source or email account to receive a callback when the account's connection status changes. You can read more about connecting disconnected accounts here.