Hi, Peggy. I have one of many possible answers for you to try. It will also be the cheapest.
If your house was vacant for a while, the water that is supposed to sit in the P-traps in the basement may have evaporated. The water blocks the smell from coming out of your pipes and into the house. The solution is to pour a gallon of water into every drain in the basement. Possibly, this is from one of the floor drains.