have you tried to reastart steam? verify files?

Go out of the beta.

where did you buy ETS2 ?

That would be a good question. SCS doesn't appear to support the legacy version of ETS2 anymore as the last update on their website for ETS2 specifically is version 1.40, which is quite a bit older than 1.55. (it's buried in their site to find it, but it is mentioned in the FAQ)

Did OP refund it?

引用自 Berks_46：

i just bought the game and im on version 1.55

According to Steam, you don't own the game, as you have no mouse icon next to your username. If you bought the game from a reseller or key seller, then talk to them, Steam is not responsible for games not bought through them.
Having a blank Steam profile doesn't help us, either.

引用自 m6dafets：

where did you buy ETS2 ?

Good question. As mojo_musica points out, Steam does not register that OP owns the game. If the game was bought outside of steam through a reseller, or worse a pirated copy, then it will not be supported here and you may be stuck on V1.55 forever. if your purchase source cant help you.