I got this error in SCCM client PolicyAgent.log after recovering SCCM primary site server.
All SCCM clients got error "Signature verification failed for PolicyAssignmentID" and thus tehy could not get policies from SCCM server.
I resolved error with three steps:
1) Deleted all certificates on primary site server in Computer\SMS store
2) Restarted SCCM server (deleted certificates were regenerated);
3) Reinstalled Management Point role.