Any ideas why I don't have any eggplants growing on my eggplant plants?

The plants look very healthy and there are plenty of buds but they never
start eggplants.

I have the plants in two sections of the garden in groups of 4 plants each
group. Close by are zucks and cucumbers that are doing wonderfully
themselves. The ground is ph nuetral with a base of clay and sandy loam
with peat and sterilized manure added in to top 8 to 12 inches over the past
10 years. Region 6b.

Thanks