OK, so I am NOT a Mac expert, and I don’t even play one on TV.
But you give a few good clues..
Previously I had uploaded the MIOS to my 64Core, currently it shows this on the LCD:
[int] N … (squares with the first one flashing)
Reverb # 1 64
So we know the processor is running and the display and wiring are good. Power supply also working OK.
MIOS Studio seems to work ok, being able to send messages to the LCD screen,
So we know that Mac MIDI OUT to MIOS MIDI IN is working, and we know that MIOS is in control of the core.
but trying to upload Hex doesn’t work. If I tick “Wait for upload request before starting upload” it never gets accepted, nor sends anything over to the core..
So it appears that MIOS MIDI OUT to Mac MIDI IN is not working, a guess based on the clues you have given.
Since MIOS MIDI OUT used to work, I doubt it’s a wiring problem.
Since your MAC setup has changed, that is the first place to look.
I would suggest a MIDI LOOPBACK test on your Mac.. You already know it can send data, so connect MAC MIDI OUT to MAC MIDI IN and send data to yourself. Then work on receiving it back into the Mac.. that should reduce your trouble area to the most likely issue.
Once you have the loopback working, you can re-connect the core and get the mac and core talking in both directions.
The above advice is NOT mac specific.. someone who knows macs can offer better advice for sure, but it’s a start.
Good Luck,
LyleHaze