Wife’s bike on turbo lost all resistance. Turbo connects up to app but pedals just spin so feels mechanical.
Taken freehub off and the metal ring holding the small plates onto the hub was in 2 pieces. Tho I can’t see how this would cause the issue (with all the small plates still in the right place).
Anything else I should be looking for? Or is that ring the cause?
Those pawls are what latches inside to make the drive work. They are spring loaded so when you stop peddling they are pushed flat.
You might be able to get a new o ring and put it all back together, but I suspect a new hub would be easier.
Yeah happy to buy new. An hour ago I thought we were looking at a new turbo.
Might even have a spare freehub knocking around.
Ta 
That kind of freehub is quite common and fairly easily available as a spare. It comes in two axle diameters IIRC so make sure you get the right one!
Edit: Novatec is the make of the freehub
