does "q vol stg=copypool" show you any volumes with a "pct util" less than
60%?

try "q actlog begind=-3 s=recla" and see if reclamation even tried to start.
If it did, do a second "q actlog" and look at all the messages right after
that time - maybe they explain why it turned off.

Then send us "q stg copypool f=d".