You are unable to connect online and receive an error code between 2124-0200 and 2124-0269.
You may receive this error code if you are attempting to use a game's online features, but for some reason you are currently not signed in to your Nintendo Account.
Complete These Steps:
Press the HOME Button to return the HOME Menu, and select your user icon from the top-left corner.
When prompted, sign in to your Nintendo Account.
Once you confirmed as signed in to your Nintendo Account, press the HOME Button again to return to your game.