I am filing as Head of Household and having the same issue. On the file review it tells me the the Cash Charitable is too large.
I was able to find the following on the IRS form instructions:
Line 10b
If you don't itemize deductions on Schedule A (Form 1040), you (or you and your spouse if filing jointly) may be able to take a charitable deduction for cash contributions made in 2020.Enter the total amount of your contributions on line 10b. Don't enter more than:
•$300 if single, head of household, or qualifying widow(er);
•$300 if married filing jointly; or
•$150 if married filing separately
