uPVC window stuck & can't opren

Annemos

This is a curved ball. From what I can see, there could be quite a bit of vegetation outside in close proximity? 

My window mechanism jammed, after my bungalow subsided from Tree Root Action. (When one pulls the handle up, a big metal hook underneath was out of line.) 

Are you on clay soil? Please just double check to make sure there are no signs of cracking inside and outside in this area. (Usually zig-zag cracks when Subsidence.)