Heroic 2.6.2 on Linux Mint: easy way to update? Also, "Game not available" error

There's a newer version than 2.6.2, right? What's the best way to update?

Also, after I install a GOG game on an external drive, it will run. Then, on the next launch, it says "Game not available." The game is still in the place I originally installed it and the external drive is on and connected. How to fix?

Thanks!