But what type: 1099-NEC, 1099-R, 1099-INT, 1099-DIV, etc? You need to contact whoever sent it to you (or was supposed to).
Do you mean a 1099-G for unemployment or a state refund?
If for unemployment, contact the unemployment agency in your state to find out how you can get one. Some states are not mailing out 1099-Gs for unemployment and you have to go online to get your 1099-G. You might want to try logging into your unemployment account and see if it is available from your account. Otherwise, you with have to contact the unemployment office to find out where it is.
As for a 1099-G for state refund, did you take the standard deduction or itemize on your federal return in 2020. If you took the standard deduction in 2020, you do not have to claim your refund as income on your 2021 return. You do not need the 1099-G for a state refund in that case. If you itemized and received a state refund and have not received the 1099-G, I would contact the income tax department for your State and find out why you did not receive your 1099-G.