It would be helpful to us if you mention your state. Best guess---MN?
That was supposed to be done when you prepared your state return, and the form was supposed to be mailed in to the state.
MN RENT CREDIT
https://www.revenue.state.mn.us/homeowners-homestead-credit-refund
https://www.revenue.state.mn.us/renters-property-tax-refund
To check the status of the rent credit in MN
http://www.revenue.state.mn.us/individuals/individ_income/pages/draft-wmr-context-page.aspx
https://www.revenue.state.mn.us/wheres-my-refund
To obtain the refund, the taxpayer must have a CRP, Certificate of Rent Paid (CRP), for each rental unit lived in during the year. The taxpayer's landlord is required to deliver a completed CRP to the taxpayer no later than January 31st of each year.
You will need the CRP to determine your refund, if any, and you must include what is called a Form M1PR with the CRP when it is filed. These forms have to be printed and mailed in to:
Minnesota Property Tax Refund
St. Paul, MN 55145-0020
TurboTax will prepare the Form M1PR for you to print. Towards the end of the step-by-step interview for Minnesota you will reach the Other Forms You May Need screen. To have the M1PR prepared and made available for printing, make sure you check the Property Tax Refund (Form M1PR) check box on the Other Forms You May Need screen, then follow the prompts through the end of the interview.
You can also file your M1PR free of charge at the MN Dept. of Revenue Property Tax Refund site, and if you're a homeowner, you can e-file it through the MN DOR's Property Tax Refund Online Filing System.
If this is for some other state, please tell us what state.