Bill, Flavor Grenade is a very late ripening pluot. I'm not sure when
it will ripen in your climate but its in the Sept-Oct range. So I
think you just need to wait on it.
I have heard that Flavor Grenade is the one pluot which actually sets
a crop of fruit outside the west coast and it sounds like you are also
having luck on that front. I have been getting almost no fruits on my
Flavor Supreme and Flavor King and plan to try Flavor Grenade as my
last attempt at pluots. It will also be nice to have a plum so far
out of the normal plum season. I have similarly enjoyed Spring Satin
which gives me plums in late June, about a month early. (Note I am
calling these plums because thats what they taste like, no apricot
flavor in them to me.)