One of the things I discovered about Hoya flavida is that it needs very little water and is sensitive to over watering. You can easily go 2-3 weeks without watering this plant, and it will be happier for it. I don’t know if this information helped me finally flower it, but it definitely made the plant happier.
When I brought the plant indoors in September, I put it into a new grow-tent that I specifically set up for species that liked it cooler. It had exactly a 12 1/2 hour daylight cycle with high humidity and temperatures that never got above 73F in the day and dropped to 64F at night. I could not believe it when I saw new peduncles form, and they actually started to bud up!