Battery icon is always at 100%, but battery level is at 0%

Hi, I have a Microsoft Laptop 4. A couple months ago it wouldn't turn on. I had it connected to a Surface dock, and tried the stock power supply and it still wouldn't turn on. I took it to a repair shop and they fixed the issue with turning on. However, shortly after that there has been issues with the battery. The battery icon on the taskbar always shows 100% but when I click into the Power & Battery settings, it began showing lower and lower battery levels, and now has been at 0% for sometime. It's weird as in that menu the battery icon always just shows 100%. I've tried uninstalling the battery driver and restarting but it doesn't take care of the problem. I now have 2 pending Surface firmware updates that I can't install because the battery level is below 40%. This laptop is 1.5 years old. It's hard for me to believe that the battery level just began sinking like a rock in a short time and that maybe the internal charger is just not working. Anybody have any ideas?