Can't get mods to work :( frustrated

[AUtigers350z]

Posting a question like this is out of character for me as I usually search and read until I can find a solution, but this seems to be more of a general issue than anything else.

I have tried to install around 8-10 mods after installing VB4. I copy the correct files to the right directories, check the file permissions in FTP, import the products correctly. Everything in the ModCP looks to be functioning properly, but nothing on the front end seems to change.

For example, the last mod I tried to install was to add extra tabs to the navbar. Tried 3 different versions from 3 different developers. All loaded correctly, had the correct options set, but none of them would work for some reason. I am using a custom style so I figure maybe it has something to do with the new style's navbar template? It's very frustrating that none of these mods will work! Everything worked great when I was using VB3 (no, these aren't the same mods, they were coded for VB4).

Any advice or someone that would be willing to point me in the right direction would be much appreciated.