Deductions & credits

I recieved my stimulus relief money (via direct deposit),but it was only $1200. When claiming my 2019 taxes I claimed head of household and I have a son who turned 16 in Jan of 2020. I thought he qualified for the $500 but I only received $1200. How do I figure this out,and if they do owe my the $500,how do I retrieve the owed money?