You might consider the KB with that error in it :)
https://support.symantec.com/en_US/article.TECH231478.html
The most common thing I have seen is when a network mapping didn't happen for one reason or another. The most common being the default option of F is already in use. (your system has a C: OS, D: Recovery E:Tools and an F: for a CD/DVD so we can't map to the express share as F:)
The other issue would be that the WIN pe environment doesn't have the needed network drivers in the boot package.
Look at what the client is doing maybe take a video of the scripts as they run and then you can see the exact reason it isn't working.