The shaver stopped charging. what is the problem?

The batteries are probably dead and need to be replaced. The correct batteries for model R-875 are available at shaveroutlet.com at the link below. You will need two batteries.

http://shaveroutlet.com/shaver-battery-pack-for-most-shavers-p-211.html

To replace, you will need to take off the back cover by removing the two screws. You can then access the batteries. The wires are soldered to the ends of the batteries. Unsolder the old and solder in the new.

If you are not able to do this yourself, shaveroutlet.com can do it for you. See link below

http://shaveroutlet.com/professional-battery-replacement-for-most-models-p-374.html