If the charger's light has never turned red while it was plugged into the wall and scooter at the same time and it has always glowed green there could be a problem with either the charger or the charger port which could have caused the battery pack's Voltage or condition to drop down to a point where the speed controller shuts off power to the motor because the battery pack is below the controller's low-Voltage cut off level.
If the scooter has been in storage for a year and the battery pack had never been recharged during this time then there is also a possibility that the battery pack Voltage has gotten so low that the charger will not charge it because it detects an abnormally low battery pack Voltage. The battery pack Voltage will need to be pretty low for this to happen and we are not exactly sure how low but if the battery pack Voltage is under let's say 20 Volts then that could be causing the charging problem. Before replacing the battery pack we would test the Voltage at the charger port to confirm that it is working and also test the output Voltage of the battery charger to confirm that it is working.
If the battery pack Voltage is above 22 Volts then we would perform a load test by monitoring the Voltage of the battery pack with a multimeter while the power switch is off, then turn the power switch on and twist the throttle to its full throttle position while someone spins the rear wheel to over 3 MPH.
The Voltage level of a good Razor E175 battery pack with the power switch off should be around 26 Volts. And with the power switch on, throttle fully engaged, and rear wheel spinning over 3 MPH the battery pack Voltage should drop no lower than 23 Volts.
The controller has a low-Voltage protection feature which is there to protect the battery pack from being discharged too deeply which would damage the battery pack.
The controller's low-Voltage protection level is 20.5 Volts ± 1 Volt. Since the battery pack Voltage is dropping down to 18 Volts that is causing the controller to go into low-Voltage protection mode and stop running the motor.
Since the battery pack's Voltage is dropping under 22 Volts that indicates that the battery pack is old, worn out, or faulty and needs to be replaced.
You are welcome. Thanks for letting us know that new batteries solved the problem.