IF(OR(VLOOKUP(J$5,$A$5:$E$68,2,FALSE)=$J$4,VLOOKUP(J$5,$A$5:$E$68,3,0)=$J$4,VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=$J$4),"a",""),

IF($I15=2,IF(AND(VLOOKUP(J$5,$A$5:$E$68,5,FALSE)="Y",(VLOOKUP(J$5,$A$5:$E$68,2,FALSE)=$J$4)),"a",

IF(OR(VLOOKUP(J$5,$A$5:$E$68,3,FALSE)=$J$4,VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=$J$4),"a",

IF($I15=3,

IF(AND(VLOOKUP(J$5,$A$5:$E$68,5,FALSE)="Y",(VLOOKUP(J$5,$A$5:$E$68,2,FALSE)=$J$4)),"a",

IF(OR(AND(VLOOKUP(J$5,$A$5:$E$68,3,FALSE)=$J$4,VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=""),VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=$J$4),"a","")),

IF($I15=4,IF(VLOOKUP(J$5,$A$5:$E$68,2,FALSE)=$J$4,"a",""),

IF($I15="","",IF($I15=5,IF(AND(VLOOKUP(J$5,$A$5:$E$68,5,FALSE)="Y",(VLOOKUP(J$5,$A$5:$E$68,2,FALSE)=$J$4)),"a",

IF(VLOOKUP(J$5,$A$5:$E$68,3,FALSE)=$J$4,"a","")),"")))))),

IF($I15=5,

IF(OR(AND(VLOOKUP(J$5,$A$5:$E$68,3,FALSE)=$J$4,VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=""),VLOOKUP(J$5,$A$5:$E$68,4,FALSE)=$J$4),"a",

IF(VLOOKUP(J$5, $A$5:$E$68,3,FALSE)=$J$4,"a","")))))

The above formula is returning the correct values when $I15 = 1,2 and 5. However when the value in $I15= 3 or 4 and all other conditions are met the returned value is "FALSE" rather than the expected "a". I have attempted to use the formula evaluation tool and didn't find it much use.

I have double checked the lookups and they're all looking in the correct place.

Any help would be greatly appreciated!