For older EN-200 Vibration meters with the non-usb charger – its important to first (a) Turn the meter off, and then (b) plug the charger into the Meter (Not the AC outlet) and then (c) Plug the charger into the AC outlet. 

 For Newer EN-200 vibration meters, the charger works just like an Iphone charger. (a) Plug the usb cable into the side of the Vibration Meter then (b) plug the charger into the AC outlet. 

Cable may be at fault. If you  have another cable, try switching cables. 

(a) Turn the vibration meter off, ensure the off switch is in the off position. (b) Plug the charger into the vibration meter, ensure its firmly connected.  (c) Plug the charger into a power outlet of 220V.AC. – The RED LED should illuminate. IF it does not, then the battery may have become disconnected – open the unit and check.  (d) The RED LED will illuminate indicating the batteries are being charged, and will change to GREEN after approximately 3 hours. 

Batteries may be dead. Recharge the batteries.