Did more digging. NONE of the Piriform products function on mapped network drives. Reply from Piriform support follows.
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Hi, Thank you for your email. Unfortunately, none of our products are able to function via network mapping of drives due to the fact that network connections do not carry the commands that we require to perform the tasks our software performs; for the purposes of security, the control that the remote computer has over the drive is very limited, and largely specified to file copy/edit commands performed by Windows itself. Even CCleaner Network Edition does not allow this to be overcome; instead of sending these commands to the mapped drive itself, it would send the signal to the Endpoint Agent software on the computer the drive is located in, and then have those commands executed locally. As such, you would not be able to use our products in this manner. I apologize for any inconvenience that this causes, and please let me know if you have any other questions, I'll be happy to answer them for you!
Regards,
John Maier | Piriform Support - Tucson, AZ