It happen to me also, the next department I went to asked my opinion on why I didn't get hired. I told them that I didn't get thru because I failed my poly. They gave me the poly, I passed and got hired.
As a general guideline you should begin with 20lb, and every 4 to 6 weeks go up 5 lbs until you get up to 40 lbs. But if at any time you feel that is too much pressure on your joints then go down on the weight.