Denise, I'll ask the questions my GF would ask, lol
Are you overwatering?
Are you pinching the suckers off?

Are the flowers staying on?
Are you feeding it?
I don't start feeding until they set fruit

Don't despair! Brandywine are not typically high yield producers around here. (especially depending on the seed source) I have 3 plants this year, and 2 tomatoes on them (which I just noticed both have blossom end rot thanks to the torrential rain). I read on the tomato forum that they take longer than others to start setting fruit.

I shake the cages around them lightly to try and help out...

My friend Lesli gave me a little brandywine tomato plant. It got huge and never even produced a flower so I dunno ... maybe it was over fertilized. She lives in Smiley in sandy soil and her's produced.

I used fish emulsion mixed with water when I first planted it to help the roots get established, but the rain has been keeping the stupid things watered - almost too well as you know. I am thinking that this is probably one of those that are difficult to bear fruit - no matter how many times I thump the blooms or try cross pollinating them. It could be the soil too. They are in amended clay soil, and I used a thick layer of straw as a mulch around them. I have never had a need to pinch any tomato plant before. All the varieties I have tried before produced without pinching off the suckers.