I felt I should add to this post to maybe help others. I too had a red light in the bottom right of the display and the unit would never take a charge. I then moved the charging clip very gently from side to side and once it made good contact, the display immediately showed it was charging. I then played with the. Lip to better understand the red light issue and I discovered it must be an indication that the clip is not yet correctly positioned. Each time I replicated a blank screen with just the red light on the bottom right, as soon as I slid the clip slightly to one side or the other, it would immediately show charging in the display.
I can see this being a problem if the battery is completely drained as the manual states it could take up to 20 minutes to get enough charge to respond, but I do believe if you see the red light, the clip is not yet properly positioned.
I hope this helps.