Hi SusanhCAS
You are right, the waiting times are extra-ordinarily long and this has not been a good point about MYOB.
As for lodging a case - hmm - that use to work quickly except I waited over a month for something that was super urgent as in getting a new client upgraded before 17 June deadline - however, once you do get MYOB's attention they are very helpful ...... alas yes sometimes way out of their depth of knowledge as I suspect MYOB are burning out helpers and the experienced ones are going elsewhere.
I have for years and years and decades requested MYOB implement a call back - where you don't lose your position - i.e. a team of helpers to answer quickly and quickly push you into the queue for the right person.... then you leave your number and you get a call back....... nope - .....
However, there is once resource you are not using - this forum - tell us your problem - exactly - screenshots (obscuring private info) and there is a wealth of very experienced, super long in the tooth partners, helpers willing to read, digest your problem and offer help - which may just solve the issue.
Reconciliation problems are well known in MYOB but that is because they are as old as MYOB's software - for years and years you could only reconcile - but never reverse - reversal is a recent add-on - so a lot of very experienced knew how to fix things.
If I can help I will - I have been fixing reconciliation problems since the 90s - what Genreve_S is suggesting is reasonable but without knowing the problem I can't advise whether it will solve things.
My suggestion - take a back copy down to your laptop and open it locally - then attempt what has been suggested - if it fixes it - apply it to your online.
Reconciliation problems are huge in their manifestations - huge and often the only way to fix is to take a backup - open it locally and reverse the reconciliation back until the problem disappears - unless the problem is years old.
The other mean trick ( I don't think you mentioned whether payables or receivables) but go reporting - and whichever it is date your report forward a year, 2 years, 3 years to see if the problem vanishes which then suggests a few things - then if that doesn't work try dating backwards until the problem disappears - then you go into the creditor or debtor account and look for the offending entry - sometimes you get lucky.
None of this causes any problem to your working file - but may give you an answer - if none of these help then it requires a more dedicated Sherlock Holmesing - and there are plenty of those on this forum.
The Doc