the plant may be adjusting to outside weather after being removed from the greenhouse, did you give the plant a few "hardening off" sessions?
i am experiencing flower drop in most of my chinense variety. caribbean red, orange hab and fatalii. last year my fatalii dropped all its flowers and i didn't get a pod. this year the plant gave me several nice looking flowers, i too tried to hand pollinate but again, as of mid last week all the flowers dropped. in my case, temperature change may be the issue as the plant sits on a window ledge and in the daytime gets full sun then night hits and on this side of the window the room is at 70F, the other side of the window could be as low as -40F (-30F was frequent). if my brain wasn't so challenged, i should have lowered the plant to the ground beside my dwc which has artificial lighting away from the window. maybe next time.