Question: Why don’t my tomato plants set fruit? The flowers act like they have been cut off.

Answer: They aren’t being pollinated.  That can happen with large-fruiting varieties when temperatures climb above 90 degrees in the daytime.  It can also happen when you grow tomatoes in areas where the plants are not blown  by the wind.  Tomatoes are self-pollinating, depending on agitation of the flower clusters to shake the pollen loose.  Try thumping the flower clusters as you would a paper wad on a tabletop.  Do it every other day and it can make significant differences in fruit set.