I also can't buy gems on the Steam version of the game. I am sent to the Steam store to approve my purchase and the store shows I have sufficient funds in wallet. But no matter what quantity of gems I chose, I get the same error message: Store Error - Store purchase failed unknown. The message is in the Arena app, not in the Steam store.
I also can't buy gems on the Steam version of the game. I am sent to the Steam store to approve my purchase and the store shows I have sufficient funds in wallet. But no matter what quantity of gems I chose, I get the same error message: Store Error - Store purchase failed unknown. The message is in the Arena app, not in the Steam store.