Hi.
Try to squeeze the clips in your fingers before attaching. They should work properly... they should fit really tight.
There are some ways to attach the Fishman:
1. You can do it normally

(but first of all - remove everything from the bridge - rosin, dust, wrong notes

. Make it clean and smooth)
2. You can attach it on the other side of the bridge (it is better, because this side of the bridge is cleaner, fits better with the surface of piezo elements). When I use BP100 i prefer this method of installing
3. You can use it Realist-like (under bridge feet) (I don't know how it works)
Of course, glue is possible, but there will be impossible to take off the pickup without destroying it.
I hope it is helpful
Warm regards
Pat