[Speedslug]

There are places that fix them but they only do insurance work from what I understand.

And those wind up with medical grade (read $$$$) work.
Us hobbyists are pretty much left to our won devices.

But keep in mind that they really are very simple machines.
There is an air compressor ( with input filters and such), a pair of cans that have a substance in them that gets "sticky" to nitrogen in the air when it is compressed, some switching valves and hoses and a purity monitoring system.

Oh and there is a "bio filter" on the output side just before the oxygen gas gets to the front panel output. That keeps any organisms from getting into the lungs of people that need oxygen to keep living.

Lots of folks forget about that last filter and it is the one most likely to get clogged.

So I always suggest replacing all three filters ( two on the input and the bio on the output) as the first step in troubleshooting the thing.

Oh and the hoses inside are replaced ever two or three years as a normal over haul when they are used as medical equipment so the ones that the machines come with can get brittle and crack after 4 years. You can get replacement hose for hobby use from any hardware store these days.

If the motor doesn't run it could be a bad starter capacitor which an electrical shop can replace for you but most likely it is a circuit breaker tripped inside it or the control board thinks that the purity is so bad it won't allow it to turn on.

There once was a website called "Franks Hospital Equipment Repair" or something like that and it had detailed overhaul and trouble shooting instructions for all kinds of brand names and models.