There's a few reasons why a tomato plant won't flower. 



So the short answer is if it is too humid, too hot (above 85 degrees F), or too dry, the plant cannot pollinate itself, so it no longer produces flowers.

It is recommended to continue to keep the plant healthy and change up the environment a bit, either move it to a less hot area, or if you live somewhere humid, you can try to place the plant in the same room as a dehumidifier, and if you live somewhere arid, have a humidifier in the same room as the plant.

Another reason tomatoes won't grow flowers is because the conditions are too good. Maturity occurs when the tomato is stressed (by virtue of a lot of sunlight or dry soil). If the conditions are low stress(consistent moisture and less sunlight), it will take longer to mature and the plant will put all of it's energy towards foliage growth instead of reproduction.

I suggest changing up the environment -- perhaps moving it outside -- to stress it out a little and activate flowering.

Hope this helps and let us know how these suggestions work out for you!