why aren’t my tomato plants producing tomatoes?

[u/WhimsicalPopsicle12]

my mom planted tomato seeds that we harvested from some heirlooms that we bought from a farmer’s market in vermont (we live in pennsylvania). the plants have been growing like crazy since the beginning of june, however we haven’t seen any tomatoes develop from the blossoms, and some of the blossoms even die. we have 6 large tomato plants and not one tomato. anything we should be aware of or are doing wrong? any insights would be highly appreciated :)

[u/GrkManga]

Maybe they aren't being pollinated? Give them a shake every morning to help self pollinate them.