I just had this issue and a turbo tax person told me to delete the donation under deductions/credits screen and then enter the donation amount under the ACA donation screen. I did this and it fixed it BUT this in turn lowered my State refund by over $100.
So I went back and re-entered my cash donation and got the same error. Next when I ran an error check the software pulled up the 1040 form Line 12(b) and I changed the $300 to $600 and it corrected it, no errors and I now have the proper refund amounts for fed/state.
