Deductions & credits

I got a letter from the irs saying I owe them money for 2021 child tax credit. I filed my taxes for 3 years through h&r block and they did not file taxes for 2021 because I don't normally file taxes because I am fully disabled. I received all but one of the 250.00 checks. Now I don't understand how I owe this money. Is it because h$r block should have filed a 2021 tax return eventhough I have no earned income credit but, I qualified for the 250.00 check. Do they need to file a amended  return with the 8812 form.