Rage 2 has a known issue that has not been addressed as yet in that the game will not start on Stadia. This bug has been ongoing for a while now and it has not been resolved. There is a workaround in order to get the game running on Stadia and it is to not allow Bethesda access to your friend’s list.
To fix this issue you need to follow the following steps
- Log into Stadia
- Click onto your avatar
- Click into Privacy
- Go down to Bethesda and do not allow them access to your friends list
- This should now work