I’ve stripped the ratchet ring out of a few shells in the past during my trials days.
Basically the steel ratchet ring is threaded into the alu hub shell in a manner that when you pedal, it tightens up the thread.
I would imagine the reason it can’t be repaired or replaced is that it won’t be able to be removed due to this threaded construction.
I have had 3 knackered hubs replaced by Hope – 2 x ratchet ring threads stripped and 1x hub shell crack due to the force I was putting through it trying to overtighten the thread, cracking the shell in half.
If you send them the hub, de-laced, it is likely they will rebuild your internals onto a new hubshell / ratchet assembly (If they have some spare Pro2s kicking about…).
it is a bugger though, as you’ll have to relace your wheel.