Basic Sum Formula in Google Sheets

Hi All,

I have a basic question. In the attached, you can see I have a basic 3 columns. The cells should be self-explanatory I hope. For the 3rd column, the blank cells represent "Unpaid".

I would like a formula that says:
a) The sum that John has "Unpaid"
b) The sum that Mike has "Unpaid"

Below is how it looks in Excel, but doesn't quite work in Sheets
=SUMIFS(A1:A10,B1:B10,"Mike",C1:C10,"")

=SUMIFS(A1:A10,B1:B10,"John",C1:C10,"")

Can anyone help? Thanks.