At some point you indicated it was a vacation home rental where you use it part of the year and rent it part of the year. If it is really a full time rental that you converted to a rental in a prior tax year then you probably messed up on that return and did not catch it so you had unallowed rental expenses in the prior year that got carried forward. If that is the situation then the 2020 return will need to be amended and the 2021 return done correctly.
