Unfortunately I've already messed with ini files, that's why I mentioned them. Anyway, I'm going to see what makes the sky work on my older installation as I haven't touched that one except it uses NewDark 1.19 and TFix 1.13.
I uninstalled to try what you did and now the sky works but not the rest of the mod, haha. FYI, I used the tinv3 you uploaded on that other forum, this link:
Tinv3 You posted it in 2012 1st October so it's possible there might have been more changes to the texture mod along the way but I read v3 was the last so I thought it would work.
This is how the ini-files, not touched by me, look like:
cam_mod.ini : "mod_path usermods+mods+mods\t2skies"
install.cfg : "resname_base .\mods+.\mods\EP\Thief1+.\mods\EP+.\patches+.\res"
In USERMODS I've 3 folders: FAM, OBJ and RES.
Anything I should do?