IFS function not working

I kept getting "N/A" in the output.

checked the help notes

"Remarks

To specify a default result, enter TRUE for your final logical_test argument. If none of the other conditions are met, the corresponding value will be returned. In Example 1, rows 6 and 7 (with the 58 grade) demonstrate this.

If a logical_test argument is supplied without a corresponding value_if_true, this function shows a "You've entered too few arguments for this function" error message.
If a logical_test argument is evaluated and resolves to a value other than TRUE or FALSE, this function returns a #VALUE! error.
If no TRUE conditions are found, this function returns #N/A error."

Since I was comparing combinations of files looking for duplicates, there were frequently no "true" result.

IFS(C4 = C3,"DUP",C4=C5,"DUP")

if neither condition is true, you get "N/A"

So:

IFNA(IFS(C4 = C3,"DUP",C4=C5,"DUP"),"")

This solved it for me. Does this help?