was your 2020 agi over $150K. then 100% becomes 110%.
it also may be due to the fact that Turbotax has not yet updated the form for 2021 which won't be until 2/24. so I would wait for the update and then see if the penalty goes away.
by the way "prior year tax liability line 8" per 2210 may not be the same as what you refer to as your tax liability. if you're interested you can read the 2210 instructions for line 8 - prior year tax liability
https://www.irs.gov/pub/irs-pdf/i2210.pdf
