This is the plant now.. But still no flowers...

Do you have a place where it can receive only morning sun? Unfortunately cestrums cannot bloom without sun. Their leaves are very delicate. What you can do is slowly introduce the plant again to the sun making sure that the plant is well watered. This plant loves water. I always make sure that the plant remains always moist and never dry. It droops its leaves very soon in sun and watering it immediately helps without damaging the leaves. Hope this helps.

It's a tropical plant I don;t understand how the sun can damage these.

The leaves are paper thin and the plant drys out fast! Tropical is prob hot with lots of humidity! not hot dry and direct sun! ( even worse through a glass window) Is there anywhere you can put it outside in a shady area maybe morning or evening sun in a tray/dish with pebbles and water and try misting/spraying it every evening