.htaccess and Permalinks

My IT guy has set things up for me, but the Permalinks have never worked.

I asked him recently to install Virtualmin so that I can set up domain names and e-mails myself.

I installed a new domain and use it for wordpress. The Permalinks work fine.

I need to know what to look for in my set up so that my IT can tweak the set up for the other domain.

Can someone point the way on where to look/tweak?