could be a lot of problems.
Could be easy to fix, could not.
Popped driver bearings usually give me the most problems. Usually the inside driver bearing is the one that's popped... on reverse at least..
Check that, easiest fix on a freecoaster in my p.o.v.
If not.. then you can check the driver and clutch.
Put the pieces on like you would but without the hub shell.
spin the driver- causing the clutch to engage. check if that works.
I pretty much doubt it's the hub shell. I thought mine was the part that was  messed up  when I had a lot of problems on my freecoaster but it's almost  99% internal problem .  check for spring  tension on your clutch.  If there is a lip at the end of the inside of the clutch(where the ball springs are at(geisha))your clutch is done. If the knurled part on the clutch isn't knurled it's done...
Another problem I had when I was first working on the freecoasters was that I wouldn't put it back together right.  Weird to explain this problem but now I put the hardware back on the non driver side   first then put it in the rim all the way.. a thing tht happened was a little bit of the inner axle would stick out of the driver side and it made pedaling awkward and it wouldn't catch well.

Sorry if my help was mediocre at best but hopefully, it somewhat helped.
Good luck..
I had bought an upgrade kit for my reverse which also fit the geisha for 20$ on amazon
I'd put the link on here but sadly :c it went back up to 81$