Yeah, so there are several possibilities:
1: There is very common problem in that the adapter plug heads actually come in dozens of sizes. They have the same overall "look" but the exterior dimensions, depth of plug, inside hold diameter, etc varies. You need to get the proper one or else there will either be a poor connection, or no connection. Or worse.... some jacks are positive (+) in the inside hole and grounded (-) on the outside edge, but not always. In these cases, if you plug in the wrong polarity plug, well you know what happens then.
2: The jack connector might have the spring contact bent and not making good contact.
3. The plug end of the power adapter might have a broken internal connection. You'll have to test with a meter to verify.
4. The jack might have a broken solder (-) joint or other broken connection.
To figure this out:
1. Test the jack head to verify that it is indeed getting power and doesn't have an internal (-) break.
2. Visually verify that there is no physical defect in the jack that would prevent the outside spring contact to plug sheath when inserted.
3. Test for continuity of jack contacts with internal circuit board. If no continuity using meter, correct the cause which could be as easy as reflowing the solder joints to the jack, or bridging broken PCB traces, or replacing jacks.