The information in this article can help you when you are unable to sign in to your Nintendo Account on Nintendo Switch and receive the error code 2124-7504.
Note: This error indicates that there is likely a temporary service outage related to Nintendo Accounts.
What to do
Wait a while and try again later.
Situation not resolved
If the issue persists, check for any maintenance notifications on the Network Maintenance page, then try again after the posted maintenance/service outage has ended.