@susan-barnett errors related to Line 30 are probably the most common error for the 2021 tax year. (Line 28 was just as bad).
if you did not answer the questions in TT correctly, then Line 30 would have been incorrect as well.
If you received the 3rd stimulus ($1400), then Line 30 should have been zero. Sounds like you received the 3rd stimulus but answered the questions in such a way that Line 30 had $1400 on it, which resulted in a higher refund that you were entitled to, so now the IRS is asking for the money back - with penalties for underpayment,
