Make sure your lookup table, $N$3:$O$119, has
an entry in column N for every conceivable
value produced by =D3-E3
Yes it has all the values
Make sure the values in column N are numeric and
not text values that look like numbers (e.g., "1").
also, check that the value in F is exactly equal to the value you expect to be found in your lookup
for example if the value is 24.9999999999999999 but is showing as 25, it will not be found via lookup if your lookup table contains 24,25,26 etc
as Mark originally suggested, it's conceivable that d3-e3 is not a whole number contained within your vlookup table
I get lots of 18.000000000000001s and 299.99999999999654 in my spreadhseets sometimes, especially after using copy/paste special/values from the results of %age formulae..... grrrrrr, very annoying
hope this helps somewhat
Chris