Are you sure that N2 contains 20--it doesn't contain a value that's formatted to
show 20?  Another problem could be that one cell contains the text 20 ('20) and
the other contains the number 20.  These values don't match.

I'd review the notes for troubleshooting =vlookup() formulas from Debra
Dalgleish:

http://contextures.com/xlFunctions02.html#Trouble

You have a response at your other thread for tips for =vlookup() and
=index(match()).

Your "matches" are not exact.

Could be decimal points are slightly off.

i.e.  formatted to 2DP  1.12  looks like a match to 1.12

But stretch 1.12 out and it may be 1.1200123 which is not a match for exact 1.12

Maybe your 20 is really 20.0000123.

The TRUE argument will return the closest lower match of 19.98

Gord Dibben  MS Excel MVP

If your "right answer" of 20 is in cell B100 for example you can put this in
some empty cell: =N2=B100  If that returns TRUE, then N2 equals B100 and if
that returns FALSE, N2 is not equal to B100.  It's just a quick check. Then
you can do further research. In your case it appears that N2 is not equal to
20 but is some value just under 20 such as 19.999999999 which when rounded
appears as 20 in the cell but does not equal 20 and the VLOOKUP, because of
the TRUE argument, finds the approximate value less or equal to 19.999999999
and that is 19.98 and returns the corresponding value from column C.
Expand the width of cell N2 and display more places of decimal to see what
is there.

Tyro

Not sure if I am reading your question correctly but I get the feeling that
you are copying that formula down a column and if this is correct, then the
lookup range should be absolute with the $ signs.

=vlookup(n2,$b$6:$c$6006,2,true)