I am looking for a way to count unique values in column E based on column M = "Installer/contractor" AND column O = {"A1";"A2";"A3";"B1"B2"}

Currently my formula is: (it only includes column M)

=SUM(--(FREQUENCY(IF('Visit Data'!$M:$M="Installer/Contractor";MATCH('Visit Data'!$E:$E;'Visit Data'!$E:$E;0));ROW('Visit Data'!$E:$E)-ROW('Visit Data'!$E$3)+1)>0))

1.PNG