HelpInvalid CD Key from steam?

I purchased ArmA II: Complete Collection on steam, but when I try to join a server with DayZ commander, it says invalid CD key then puts me in a pool. I can then press continue/start and it will start a game and sometimes I still see red messages (server messages).

Does this mean I am not connecting to the server and I am playing alone? Or is it fine and there is no problem?

The key is just fake basically all you need to do is take a picture of the key in steam and they should replace it

Nope, just open ARMAII - close and then ARMAIIOA - close. Now Your key should be valid

if you dont figure out how to fix it then message steam support