Internal battery replacement – check
PMU reset – check
PRAM reset – check
NVRAM reset – check
Computer starts up on the table, with only one monitor and a keyboard and mouse connected – check
Retains time and date – check
Start up in the enclosure with one monitor, a keyboard and mouse connected
Start up with Ethernet cable attached – check
Start up with ProTools cables attached – check
Open PT software – check
Shut down computer and plug in monitor extension – crickets
Pull G4 out of enclosure and try to start – crickets
Sounds to me like the problem is with your flux capacitor.
Say you take up another hobby like occasionally streaming a concert? That might run nicely on a new Mac. New Mac could also be used for recording/mixing new albums. Two hobbies, one piece of hardware, 20 more years!
Ha ha ha ha! I just watched Back To the Future the other day!
OK, Ottmar. This is IT – no pun. Donate your G4 – get a wonderful new Mac. Governor Grisham has announced retailers are opening now at 25% capacity, and Best Buy has curb delivery service also. You probably know better places to shop. I have had my iMac 21.5 screen since 2013. It is wonderful and has had zero issues of any kind. I have only added an external backup disk. I like not having a separate tower, but you might need the Mac Pro. DO THIS for you and for us.