It's difficult to hazard a guess without specific information. File names. etc. My first suggestion is to check your new Aircraft.cfg entries carefully. Make sure you renumbered the [fltsim.x] headers correctly. Even a small typo can cause the new variations not to be listed on the menu.
I checked but I'll take your advice and go through them again. Thanks.
PC6_KLU is the file name on all three and the author is Rene Spaan. One is Tigerrmeet, Camo and one other. I've given up. :D
A search for > pc-6c Rene Spaan < brings up these files.
http://simviation.com/1/search?submit=1&keywords=pc-6c+Rene+Spaan&x=16&y=9I've installed the Pilatus PC-6C H2 Package + the IFOR, Tigermeet & Camo textures. All work fine as you can see.

Make sure you carefully check the [fltsim.x] numbers of previous variations you installed as a mistake in one of them will prevent following entries showing up. If all else fails copy the complete [fltsim] section from your Aircraft.cfg & paste it here. I might be able to spot any errors.