If you paper filed both returns at the same time in separate envelopes then the 2020 return was simply processed first for any number of reasons. Maybe the department processing the 2020 return was faster than the department that handles the 2021 returns. Or the 2021 return had to go thru some kind of manual checking. There is nothing you can do but wait patiently and check the IRS once a week for an update and don't count on the refund coming anytime soon as paper returns are taking 6 months to a year to process.
