Passion Flower Bud Drop

I purchased a passion flower vine this spring. I kept it in a pot for the summer, outside. When I brought it inside in September, it started producing large green buds. The first one started turning yellow over a couple of weeks, then it dropped off without flowering. The leaves of the plant have a light yellow mottling on them. There do not appear to be any bugs. What am I doing wrong? The plant was in full sun all summer, and is now in a sunny south window.

Taking the plant indoors represented a huge change in conditions and as a result the plant is dropping buds in order to get used to the new conditions first. If after about two months or more conditions are still right for flowering, then it will probably try again.
The yellow spots on the leaves could be spider mites. These pests multiply very rapidly under warm and dry conditions. Spray with pyrethrum soap spray to control the population. After the number of pests is down to negligable numbers spray the plants with a hard stream of cold water every three or four days. This will keep the numbers down.