Is your green house totally enclosed? Without pollinators there is no point in having flowers anyway. I havne't heard of this but, there might be an association between a chemical stimulant from pollinators and flowering in tomatoes. Just a hypothesis though.
Also, try using organic fertilzers. I throw a handful of kelp meal (blood meal works as well) down around the plants then fertilze weekly using liquid fish one week and liquid seaweed the next. Follow the instructions on the bottles.
I also work manure into the soil as well. Does the trick!
Hope this helps and have fun with your tomatoes.
Feed the soil, not the plants.