Perhaps the IRS changed something else on your return (such as your income), which in turn limited the charitable contribution. Wait for a letter from the IRS; they do not notify TT.
We got the letter from the IRS. They did not change our Adjusted Gross Income. They changed the charitable deduction down to 60%. IRS Publication 52 - in discussing the 100% limit for 2020 for cash contribution - states as a requirement that "The taxpayer elected to have this limitation apply to such contribution." TurboTax Deluxe did not have a question about selecting the limit. How do I know if our file was transmitted with the selection made? Turbo Tax online doesn't even recognize that we've already filed our return and the IRS accepted it!