What if the account name is blocked?

First, make sure to have a good backup before attempting any changes in case something goes wrong.

Here is an Apple article with instructions for changing this information, but be very careful to follow all the instructions very carefully or you will have a mess that will take even more work to fix:

Change the name of your macOS user account and home folder - Apple Support

You should always have frequent and regular backups of your computer and all external media (including the cloud) which includes important & unique data.

Far too many users who attempt to change their account-name and home directory end up completely locked out of their computer.

Be CERTAIN you have an additional other ADMIN account that you can use to log in if this account gets damaged in the process.

Overall, It is more Prudent to create a new account and migrate your files and settings.

Hi,

You'd better create new account, instead of changing account name and the home directory.