I have the same issue and same message. No indication of how to contact MYOB. Chatbot told me it is out of hours and it can't help. Tried switching off ridiculous AI tool but still I can't apply transactions to an account manually. Tried logging out then back in, refreshing etc. Nothing works and BAS due tomorrow.
Very cross about yet another increase in monthly fees yet no support when needed. Constant changes to the look, feel and services provided by MYOB requiring constant re-learning of software. Businesses don't have time for this. Every time there is a software "upgrade" they should provide a month free as businesses are otherwise incurring downtime costs of staff having to relearn software.
Will be looking elsewhere for next FY.