Yes. If you were billed and allowed to pay in December, for tax purpose you are considered enrolled. You can claim the tuition credit for 2020. Answer that you were enrolled.
Since you actually paid in 2020, technically you would not be allowed to claim the credit, for that payment, on your 2021 return. When it asks if you had a 1098-T, answer that you qualify for an exception.
That said, it's unusual that you didn't get a 1098-T, since you paid. You may need to wait a few more days. Check you student account on line; it may be posted there
