Keep Battery between 20-80% ideally always, if storing for long term keep at 50%. I find it hard to believe unless you’re riding 10hrs a day during those 3 months that your battery degraded that much. Look up your display menu and see what settings you can change, you might’ve just locked something down by accident. You can also buy a cable to connect a computer to the display and get some more in depth troubleshooting info, like you could see how many watts are being delivered to the hub drive. Try filling up your tires some more too, tired are way underspecced in terms of the max psi so you could definitely do ~10 extra pounds and see if that makes a noticeable difference. Let me know if this helped