Hi HmmmReally
This is very sloppy coding by MYOB - not uncommon - and the fix to fix a fix that wasn't actually broken is now causing more grief than 'just leaving things alone as they were'.
Their seems to be many work arounds for this problem but all involve that clients doing something for 'each user' - and the fault recurs every time they roll out an update.
The registry fix re HKLU & HKLM does work but it is pedantic - it seems you need to sometimes be an administrator - notwithstanding - it is quite unreasonable for MYOB to create such a mess and to leave it to 'the client' or 'client's IT department' to sort out - jeez MYOB this is messy please come up with a universal fix.
I do not have time to deep delve and work it out for myself - but it seems your writing to registry is somehow problematic - or not writing.
And writing to registry may have worked previously to not cause this problem but Windows Security is evolving to make this a harder thing to do - and what works on 1 machine or another just doesn't work generally - ........ fix this MYOB this is a mess - notwithstanding it coincides with your shutting down of local file access, hmmm really messy MYOB.
The doc