You probably need to get back on the phone with an agent. If this is a program bug, it’s going to be practically impossible to diagnose it in this forum. When using TurboTax online, you are not allowed to view or edit the programs‘s internal worksheets or calculations. A customer support agent may be able to help you with that. If you switched to using the desktop version installed on your own computer, you would have access to view the forms and calculations and it would be easier to troubleshoot.
According to the 2019 version of IRS publication 526 which discusses charitable contributions, carryovers are subject to the same percentage limits when they are used as applied in the year of the original donation. However, the publication 526 also says that you were supposed to apply current charitable donations first, and then use any available carryovers. That should mean that you would fully deduct your cash contributions for 2020 and then could not use any of your carryover because you have already exceeded the 60% limit that applied in 2019. The IRS has not released the 2020 version of publication 526, so it is possible that the rules have been modified or the calculation has been changed because of the temporary increase in the charity donation limit.
Here is the link to the unofficial draft version of publication 526 for 2020.
https://www.irs.gov/pub/irs-dft/p526--dft.pdf
You can try and do the worksheet yourself and see what you come up with, but as I said, because you are using TurboTax online, you can’t access the internal program worksheet to compare it.
