Wait a minute ... do you mean you filed your return with an amount on line 30 of the form 1040 for the missing stimulus money? And the IRS did not send the refund but instead sent a bill ? What that means is that they do not agree with you ... they say you did get the stimulus money so you cannot have the credit on the return.
If that is the case then you will need to put a trace on the missing stimulus money they say was sent ... https://www.irs.gov/coronavirus/second-eip-faqs
