Steam API is currently reporting outdated information to our servers, therefore some users can not register in TruckersMP. As the issue is out of our reach, unfortunately, there is nothing we can do to resolve the problem.
If you experience that, please try again later. Apologies for the inconvenience.
BEFORE CREATING A TICKET
Steam currently has some heavy issues with their API. Due to these issues, you may experience some problems at TruckersMP with linking games / DLCs to your account or even creating a profile. There is nothing we can do right now. We hope Steam will fix that issue very soon.