No MIDI after opening old project

[Timeline]

All MIDI from keyboard gone. Have usb plugged and MTP-AV yet it reads as woking in MIDI monitor on the usb. No MTP though. HELP! This happened suddenly after months of everything working. Is this an Apple thing?

[stubbsonic]

For me, I often have to open AudioMIDI Setup and re-connect my keyboard to my interface. This happens all the time. No MIDI input (even though I can see everything hardware wise is correct). But AMS just decides on its own that my keyboard isn't the one I've used forever.

You can also try clicking the "rescan MIDI" button, at the top of the AMS window, which somethings gets it all working.

[Timeline]

Tried rescan. No luck. Will try unplugging the power cable to the machine and USP plugs. You might have something there. Regards and thanks.

[stubbsonic]

When I said "reconnect" I meant those virtual "cords" within the AudioMIDI Setup MIDI window.

[Timeline]

Yes, I tried that and it made no difference. BUT

what I did to solve it was this: Unplug the mac from AC for 10 minutes plus the MTPAV USB so all Mac USB ports could be reset.

That brought it all back, the MIDI keyboard and the MTPAV.

Recovered MIDI but why are my USB ports going down on occasion?

Ans: After visiting Apple discussions I found out that overloading MIDI ports with too many devices causes this. The fix is to add powered USB hub to chain. Thats next on my list.