It appears this is caused by the troops.txt. It works for me, but it looks like the game's engine thinks you a cheating with the modified .txt. You can fix it by either:
a) Use the Restore Files folder in the Westphalian Pack download .rar, and replace everything. Then, if you do wish to have the units, extract the mod again, but just extract the Textures folder (not the troops.txt).
b) Download a updated one
here, I have worked with the .txt and tested it, the engine shouldn't think it's cheating anymore