The size of your refund is the function of many things, and since we in the Community cannot see your private tax data, we would just be guessing in the dark.
But if you used the TurboTax Live service, they would do is the same thing that we would do if we had access to your tax data - we would compare your 2019 and 2020 returns line by line until we found an apparent discrepancy.
If you would do that and have a question about it, then came back to us to see if we can clear something up for you.