Bought the game yesterday.
Played only 2 matches, and since then I constantly getting error "Steam authentication failed" when trying to connect server.
I tried to fix it by myself, but no luck.

Is it going to fixed, or should I refund?

Fixed with Workaround#2 from this topic:
https://steamcommunity.com/app/581320/discussions/2/1742228532896888962/

Hope devs will fix this bug eventually.