When i want Start Mission or online fight say the Game one Monster is incorrect …i have Chance all my Monster but this error come ever what i can do?
This most often occurs if someone is using a hacked game. If that’s the case I suggest you buy it. If not, post a screenshot of your monsters here.
No tue Game is no a hackt Version… i have only write with tue Support that she give me my old Account Key why i have forget. Tue Support habe help me but the Monster i cant use online -.- and i have buy the Game for One or two years 
Find out which monster it is by removing monsters one by one and trying to go online.
If your account is actually legit then message support about that one(or maybe 2 monsters).
This was an issue a while back.