#N/A in this situation would mean that no match could be found in
column G of the lookup table. You could trap this using a construction
like =IF(ISNA(lookup_formula),"no match",lookup_formula).

Your vlookup formula has a third parameter of 1, meaning to return data
from the first column of the table - presumably you intended this to be
2? If it was set to 2 and there was a match on column 1 of the table
but no data in the adjacent column, you would get a returned value of
0, even if the cell was empty.

Hope this helps.

Pete