Bob Phillips wrote...
=INDEX(L1:L100,MATCH(40066&80964,K1:K100&Q1:Q100, 0))

which is an array formula, it should be committed with Ctrl-Shift-Enter, not
just Enter.
....

An alternative that doesn't depend on fixed width fields in columns K
and Q,

=INDEX(L1:L100,MATCH(1,(K1:K100=40066)*(Q1:Q100=80 964),0))