I highly doubt any major corporate franchise is going to risk repairing any of their own industrial machines or have a 3rd party do it, without a warranty.
Taylor already said McDonalds franchises are free to fix the machines themselves but it breaks the warranty. This is usually for a good reason.
This isn't even a question of repair. Mostly what they need is a tool that gives them human readable error messages so they can correct whatever minor issue that they'd be told to correct with a service call.
As others mention most of the problems seem to be tank is too full or not full enough to complete a heating cycle. Most consumer grade machines would just display that directly or at least list the error code in the manual, the McDonalds machines don't.
Taylor already said McDonalds franchises are free to fix the machines themselves but it breaks the warranty. This is usually for a good reason.