Just a warning to hopefully stop anyone having the same issues I did. I tried editing launch settings to skip the 2k launcher on a game and it crashed. I didn't think anything of it then tried to reload the game and got an error code. I decided to play something else and got the same error code, after this none of my Steam games would launch on GFN.
Turns out if you try to edit launch settings on any game, Geforce Now will block you from launching any steam games, even the ones you haven't played, or edited the launch settings for.
The only way to resolve this is to contact them through the official support channels and wait a handful of days for Tech support to manually reset your account, then you have to re-sync your Steam account before it'll work again.