Hoya polystachya IML 1043 has not flowered for me in a long time.  I brought it to my office area where it got too much sun and very dry air about two years ago.  It just sat there and got sunburned, and looked very sad.  I brought it home this spring and it immediately picked up.  It is in the greenhouse for the summer where it is now growing new leaves and flowering – welcome back old friend!