If a profile doesn't show up, it's probably due to a problem with the profile, but the real cause is more likely to be found in the save!
So far I've found two reasons why it could go wrong.
1. Purchased accessories that have not been properly removed from the save. In other words, removing a mod for accessories without selling them first.
This applies to the player truck and the trucks in the garage.
2. Using an email address instead of your username for a profile associated with World of Trucks.
It is possible that there are more reasons but I think it is more than likely that the cause of the problem can be found in the game.log.
Even with and the exact line where the problem is mentioned.
Ever since I tried to avoid these two things, I haven't had any problems with profiles not appearing anymore.