There seem to be some issues with the MTX in full offline mode.
I first accessed the game online to enable the MTX for offline mode. If I then start full offline the first time, it seems to work fine. After equipping MTX everything looks good.
However when logging out of the game and logging in again (full offline mode), pressing the “play offline” button does not do anything (does not forward to the character selection).
If I login via the standard login and select “offline” (not full offline mode), unequip all MTX on my character, I am able to login via “full offline” again.