Rocket League license agreement?

Have a problem. I want to play Rocket League with friends, but it always says

"'Username' did not accept the license agreement".
Name isn't against guidelines or anything either.

He's playing on the Nintendo Switch.

Maybe he should link his Nintendo account to an Epicgames account.

If he doesn't have one, let him create one quickly.

Has already been linked.

Maybe also buy the game on the Epicgames account?