Go back to My Info on the left side of then online program screen and make sure the filing status is Single and edit if necessary.
Or if using the desktop editions go to Personal Info to check and edit the filing status if necessary.
If you started the return filing jointly and are now switching to single then you will need to remove the spouse's income if you entered any ... just changing in the MY INFO section will not remove everything.
Did you get divorced in 2021? You might need to start over in brand new account and not transfer from 2020. Or are you married and want to file Married filing Separate?
How to start another return in the Online version