Please clarify your question. I believe you may be confused about who is asking the question. The IRS would not be asking questions about a homestead credit, by your State Department of Revenue could be inquiring about a homestead credit that you may have claimed. Double-check where you saw this information and submit another question with more information.
Also, all you need to provide the state is verification of your rent. You should be able to get whatever certificate they are asking for from your landlord. Check with your landlord to see if he can provide the certificate being requested.
Also double-check the year. Is it for 2021?