Apparently Hoya spartioides flowers open up at night and only last a few hours.  The last time these flowers opened for me, I had enough time to photograph them in the morning, but this time they were already closing up before I got to them.   The next time I get this plant in bud, I will need to check it in the middle of the night to get my photos!

Hoya spartioides Flowers on the Way Out, But Still Beautiful – October 2014