Return Code 1639 when attempting Task Sequence client installation via MDT

Hi,

I'm trying to install SEP client 12.1.7004.6500 on Win10 via single application in a task sequence. After the deployment completes, it comes back with:

Application Install - Symantec Endpoint Protection - x64 returned sn unexpected error code: 1639

I'm using the same command line that I use for the SCCM installation that's working nicely:

msiexec /i "Sep64.msi" /qn SYMREBOOT = ReallySuppress

I have another msi application (NetSupport Notify) that is returning the same error upon completion of the deployment, and another msi application that is installing fine. Any advice is appreciated!

-GB