This solves the problem for all users. Before playing Rocket League, you must accept a licensing agreement. This license agreement is updated occasionally, which requires players to give their consent each time. If a player does not finish his game from time to time, he will probably come across an error preventing him from playing because he has not accepted the new license. For some reason, some Nintendo Switch users were unable to resolve their issue with the license agreement even after restarting the console itself.