Did your client qualify for the CA EITC? That would show right above, on line 75.

So if you have a credit on line 75 and they have a child under 6 yrs old, then the YCTC would apply as well. They have to meet the CA EITC first in order to get the YCTC with a qualifying child.

The California YCTC? The child needs to be under 6 years old (5 or younger) on 12/31/20 to qualify, are you sure youve entered the date of birth correct in both programs?