Apple iPhone XS Max will not charge or charges slowly

An iPhone XS Max that does not charge, or charges only sometimes, almost always has lint in the Lightning port, a worn cable or adapter, or a battery that has aged. The XS Max uses a Lightning port and supports Qi wireless charging, so you can test both: if wireless charging works and the cable does not, the port or cable is at fault. Look into the port with a flashlight; pocket lint packs in over the years and stops the cable seating, and a wooden toothpick removes it gently. Try another cable and an adapter that is Apple or MFi-certified, and another outlet. A phone that was flat for a long time can take several minutes to show the charging screen.

If the screen says Not Charging or Accessory Not Supported, a non-certified cable is the usual cause. After cleaning the port, check the cable end too: a Lightning plug with a bent or worn connector will not seat. Apple's own cable ends should show no discoloration or looseness. A seven-year-old iPhone has often had its battery replaced once, and a replacement fitted by a third party can behave differently: the phone may show a message about an unknown part, charge slowly or fail to report battery health. If your phone's charging trouble started right after a repair, go back to the repairer first, since a badly fitted battery or a damaged flex cable is more likely than a fault in the port.

Apple's own service can inspect the phone and replace the battery with a genuine part.