This KB describes what can be possibly done when no verification strip is printed below the job (although verification was enabled).
It might be related to a bug which forget to copy the strip from the ProofFolder share on the Imaging Engine system to the ProofFolder share on the Proof Server system (in case Imaging Engine and Proof Server are installed on a separate system). In this case the location of the strip refers to the ProofFolder share of the Imaging Engine system which can't be accessed by the Proof Server service account.
Symptoms
Verification is enabled in the Pack Proof ticket.
No preview of the strip is showed below the job in the Proof Client.
No verification strip is printed below the job.
Solution
This issue is solved in Pack Proof 16.1.
Workaround
Add the BGSYSTEM account to the Proof Server service as explained in this KB: