Form 1040 line 11 is your Adjusted Gross Income (AGI). You can't enter it because it's calculated from other information on your tax return. Line 11 is line 9 minus line 10C. Why do you think it should be zero? Did you have any income in 2020? If so, line 9 should be your total income. If you did not have any income, why are you filing a tax return?
