What operating system are they running?
What do you mean by office? Is this a LAN environment with a shared mapped drive?
If so, can they see the mapped drive when they browse to the file from the login screen?
Are they navigating to the GLGLOB.xxx file and seeing it there to select? Or are they just using a remembered path to log in?

Sounds like the extracted zip is not writing all the files to the network drive. Or perhaps, the AV is quarantining some of the files?