I am getting a similar issue with roundcube. Mailboxes are created in Sentora and work using a different email front end (Rainloop) and not roundcube. I haven't really looked into it aside from noting that the accounts are not being made in roundcube's database, but maybe these are related somehow or similar in nature to the cause. Have check through just about every related log file and nothing of interest.
It was all working fine for over a year until about 4-5 months ago.
It was all working fine for over a year until about 4-5 months ago.