You don't need to amend for that. Amending won't change the tax due or refund. You owe the tax due. You can Pay the IRS directly at
Https://www.irs.gov/payments.
The state return has nothing to do with the Recovery Rebate Credit on line 30. Must be something else for state.
You can go back into your return to check your entries and answers. But be careful not to change anything. Click on Add a State to let you back into your return.
That is the list of generic reasons they give if they changed the Recovery rebate credit on line 30. How much is on 1040 line 30?
Did you not get the 3rd Stimulus payment? Or qualify for more? Line 30 is only if you didn't get the full amount or qualify for more. The IRS shows they already sent it to you.
Double check your bank statements and Check your IRS account (both accounts if married)
Your Online Account | Internal Revenue Service
If the IRS thinks they sent it to you but you didn't get it request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
