Error code 2021-0003 is displayed while using Nintendo Switch.
Applying system menu version 5.0.0 or higher will help this error from occurring.
What to Do:
Ensure your console has the latest system update.
If the console is already up to date, restart it by holding down the POWER Button for three seconds, then select "Power Options" > "Restart."
If the console does not respond, hold down the POWER Button for twelve seconds to force it to shut down, then power on the console again.
If the error is still occurring with downloaded software, check for corrupt data.
Depending on the system menu version, a system update may be required for this option to become available.
Complete These Steps:
From the HOME Menu, select "System Settings."
Scroll down the options on the left and select "Data Management."
On the right-hand side select "Manage Software," then select the software you would like to check.
Select "Check for Corrupt Data."
Situation Not Resolved:
If you would like further assistance with the Nintendo Switch console, please contact Nintendo Customer Service.