There was an issue with the EGS version of the game that we fixed over the weekend for the most parts ((EGS) LOTA DLC no longer available + stuck on loading screen). Unfortunatelly not with 100% success and in some cases this is the follow-up problem. We are aware of it and are preparing another fix. We apologize for the problems.
If you get this error message and verifying installation does not help you can send us report by pressing F10 at the moment when the error message appears.