IF & VLOOKUP to match months and return value

Hi

I was attempting to match data from table 1 with data from table 2 and return the corresponding value. I have been using the following formula to no avail. Can you please assist.

=IF(ISERROR(VLOOKUP(BG2,$BR:$CB,1,FALSE)),0,VLOOKUP(BG2,$BR:$CB,1,FALSE))

I have attached the excel file.