I believe I know your problem, as I had similar problems with my network. Whenever I tried to execute the login script from clients, it wouldn't locate the groups I had mentioned for my drive mappings. What I did to fix the problem was mention the domain name along with the group name, as I think the clients were attempting to look locally for the groups. Here's an example:

If InGroup ("DOMAINNAMEHERE\Domain Users")
Use K: "FILE SERVER\FILESHARE"
Endif

So if your domain name is Yahoo (which I'm pretty sure it isn't :-)), it would look something like this:
If InGroup ("Yahoo\Domain Users")
Use K: "FILE SERVER\FILESHARE"
Endif

Let me know if I helped, as I'm also a beginner with very little experience with programming/coding, so I would feel great to know that I helped someone else out instead of everyone just helping me.

Good luck
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'I have often regretted my speech, never my silence.' Xenocrates (396-314 BC) Chris Jorgan