If both fail, inspect the charging port with a flashlight.
4a) If it looks dirty, try cleaning it out with a toothpick (if you have a dedicated plastic tool for mobile repair, use that).
4b) If it doesn’t look dirty, refer to 4a. What often happens is that lint from your pocket compacts over time as it gets in there and then gets pressed in by the charger.
If this doesn’t work and you have a good, locally owned mobile repair shop nearby, they might look at the port for free just to see if there’s anything you missed.
Only after all of this would I start to strongly consider the phone itself as the culprit.
Only after all of this would I start to strongly consider the phone itself as the culprit.