System.ArgumentException: not a pack file
I'll show you the code that triggers this error:
Code:
char[] signature = reader.ReadChars(4);
if (new String(signature) != "PFH4")
throw new ArgumentException("not a pack file", "filepath");
As you can see, this happens when the pack file signature is not "PFH4". As all of the packs for Rome 2 have the signature PFH4, it can only be a mod that doesn't have.
I suggest someone with this error gives me a list of the mods they are using from their data folder. Cheers.