I don't know what section you're working in, but I've done the backdoor Roths for a number of years including the 2021 tax season and I never have any problem. If you're taking money from a traditional IRA, its identity is spawned by the 1099R that you get associated with the Traditional IRA - it shows a withdrawal (Wages & Income section, then Retirement Plans and Social Security sub-section). Your 1099R should show that the amount is taxable, etc. After you put that into the section associated with 1099Rs, it'll ask you how much of the withdrawal amount was used to roll over into another Traditional IRA or to a Roth IRA. You should be able to put any amount up to the total amount that you withdrew, minus any taxes that were withheld.
Could you be taking money from a non-IRA account and put it into the Roth? That can't legally be done, and you'd have to work with your brokerage house to reverse the action. A Backdoor Roth is done by converting moneys from a Traditional IRA into Roth IRA. It's technically a Conversion from a Traditional IRA to a Roth IRA.
Could you have taken it from one Roth account to another Roth account? That would show only on a form 5498 and you wouldn't even get a 1099R.
I hope the above helps. I've been retired for over 10 years and Conversions from my excess traditional IRAs to the Roth version has been high on my tax conscience ever since, especially since my RMDs have started. My income at this point is $0, except for Social Security, and Annuity (Roth, by the way so that's not taxed), and investments. Maybe you should be sure to put in any "income" you get from investments first if you haven't already.
Hope this will help.
