My Morning Glories are not blooming, the vines are tall and thick but not one bud, I live in Saskatchewan ,Canada

Question

South facing , in front of a window,someone said I should not use fertilizer

Answer 1

That is true. They don't need fertilizer and they prefer average to poor soil.

These two articles will help you determine what you need to do:
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/morning-glory-not-blooming.htm
https://www.gardeningknowhow.com/ornamental/vines/morning-glory/prune-morning-glory-plants.htm