Hinge not keeping lid open?

Unfortunately there are so many different types of cooker it is difficult to give specific advice without you letting us know the make and model of your cooker.
As a rough guess, I’d suggest that you pull out your cooker and take a close look at the hinges from the rear, you may find that there is an adjustment screw to tension the springs that will be attached to the hinges. You may also find that one of the springs is no longer attached, which could mean that you would need to replace a broken part.

Rupert
October 2020