I've resided in a foreign country whole 2020 and at the time of filing. At principal residence info, I left county field blank "No Entry" but didn't go through by error.

I put my foreign address as the principal residence, and put "no entry" in the box of your county in California. Then error message shows up" please enter your county of principal residence".
No matter  I check or blank at "County is outside California", it didn't go through.