Apple iPhone 11 Pro Max will not charge or charges slowly

The checks in more detail

Look into the port with a flashlight; years of pocket lint pack in and stop the cable seating, and a wooden toothpick removes it gently. If wireless charging works and the cable does not, the port or cable is at fault. A message that says Accessory Not Supported points at a non-certified cable, and a Liquid Detected alert at moisture in the port, which needs drying. A phone that was flat for a long time can take several minutes to show anything. A battery that holds no charge needs a replacement. A force restart clears a stuck state.

If the phone charges on a computer's USB port but not on a wall adapter, the adapter has failed; try an adapter you know works with another phone. A very cheap or old adapter may not supply enough current for the 11 Pro Max under load, so the phone charges slowly while in use. Using the phone for video while charging on a weak adapter can even lose charge. If the phone only charges with the cable at a certain angle, the cable's plug is worn or the port is full of lint, and cleaning plus a new cable usually fixes it.

Avoid pulling the cable by the cord, which weakens the connection, and replace cables every year or two if you charge daily. Remember that Lightning ports on a phone of this age are well used, and a socket that has lost its grip can sometimes be tightened by a repairer for a small fee, which is cheaper than a new phone. If you rely on the phone for navigation in a car, a loose connection while driving can drain the battery, so address a flaky port before it becomes unreliable.