I see the error, and I initially advised you incorrectly.

Your lookup range has to encompass all of the data you are looking in. You have:

=VLOOKUP(B2,Sheet2!$A$1:$A$2000,2,FALSE)

It should be

=VLOOKUP(B2,Sheet2!$A$1:$B$2000,2,FALSE)

Notice the lookup range has changed from A1:A1000 to A1:B1000