Welcome.
Some possible causes:
- Faulty battery or bad battery connection (even when plugged in, battery must be fully operable for many devices to turn on)
- Incorrect or faulty cable or charger (some devices, especially tablets, require more power than others and may use additional conductors in the USB cable that are not normally used for charging; it might be enough to light the red LED but not enough to actually charge)
- Failed power button
- Other more severe failure
Try removing and reinstalling the battery if it is removable. Try the original charger and cable that came with it with another device to make sure they are working properly, then try them with the wm8650.