I bought a mandevilla last week and all the buds fell off :(

What is the temperature at night time?Did you re-pot the mandevilla or check to make sure it is not pot bound?

Mandevilla is a tropical plant that we grow here in Florida. It sounds like it's in shock. It needs warmth and full sun. You don't say how long you've had it, how much you have watered it, the temp outside, your zone, etc.

I have only had it about 1 week. We are in zone 5 so it will not go outside until warm and under my canopy. I have it sitting in a pot into which I put the water. The soil feels cool and not dry. I am going to move it into west window when I move some plants. My dipladenia I have had for years and it has never bloomed. Lots of runners which die back all the time. It is in a west window and I water from the bottom. Thanks for helping.

Sounds like it will be fine ,but your piece of mind check to make sure it is not pot bound for the benefit of the beauty.