How much fruit & sugar did you put in there? And did you do this in 2 steps (first, boil the peels in water with the seed bag, rest overnight, and boil with sugar on day 2)? Doing the 2 steps helps extract additional pectin which helps the jam set.
How are you testing it? (using a small metal spoon in the freezer works well)
How energetically is it boiling? I find that you need a fairly robust boil (avoiding scorching of course) so enough water evaporates. Constantly mixing helps. Do you know the current temperature?
What type of pot are you using? Something wide will get you there much faster.
Feel free to post a picture or video if you can, seeing the bubbles is another indication for how close you are to the gelling point.
