are you trying to delete "local Folders" or whatever you have renamed it to, a special account?

Is it your only account? If so, it will also be your default account, which you're not allowed to delete.

If/when you have more than one account set up, nominate another account as the default and this one should become removable.

Another possibility is that you have inadvertently renamed your Local Folders account , and you're not allowed to delete that one either.