Rome II ignores mods

[Destin Faroda]

Hi there,

I'm trying to make a mod compatible with the current Rome II version. However, for some strange reason, I can't test it as the game won't load it. Whatever I'm doing - creating a user script file, clicking "load outdated mods", changing pack file to movie etc. - the game simply ignores it.
Did I miss something or is that yet another error from CA?

[LEXI2016]

In your rome 2 menu go to options, then mods & make sure both boxes are ticked.

[Destin Faroda]

Both boxes are ticked.

I just discovered the mod log which has the following to say:
_r2tr4.pack
this file doesn't have a valid pack header; rejecting it

Fascinating. I created this pack file via the Assembly Kit (BoB). Another up from CA?