Built my e-bike with a complete kit from Johnnynerdout and it was awesome. I 29er Specialized with disc brakes and front suspension. After having it sit idle over the past winter, I put it on the charger and it still shows 4 green lights on the battery, however the control unit on the handlebar does not start up when the battery is switched on. Any ideas on troubleshooting this issue? Is it common for the control unit to go bad or is it more likely a battery issue? The build is only a couple years old (2023)