Test the charger piece first with a voltmeter; by unsnapping the black cover you can gain access to the inputs of the cable receptacle. The otter pins are where the voltage flows looking at it with the small side down the pins are 1-5; positive is pin 1 and ground is pin 5 you should get 4.5-5.5 volts through it. In reading your post again this is likely your culprit if the solar charger does charge it. I've many of these come in with corrosion at the receptacle.