=SUMPRODUCT(--ISNA(MATCH('Master Client List-do not
edit'!D3:D65536,{"Jason",Michael"},0)),'Master
Client List-do not edit'!I3:I65536)

Marina wrote:
I am trying to sum column I based on the rows that do not have either Jason
or Michael in column D.

=SUMIF('Master Client List-do not edit'!D:D,"<Jason""<Michael",'Master
Client List-do not edit'!I3:I65535)

However, the above formula is giving me the results number of unique #rows
not equal to Michael and #rows not equal to Jason (i.e. all rows because it
sees it as an OR rather than an AND).

What is the correct formula?

Marina