Hi John
I am not really sure what might be going on here. Some possiblities come to mind, but I am not sure which one might fit your situation. It is possible that you just haven't waited long enough for the buds to open. The plant could be in too much shade and that might be slowing flower development. Morning glories tend to be open early in the day. Any chance you are looking at your plants late enough in the day that the flowers have closed?