I have the answer to your question, finally. I’ve got the same bike with 700 battery.
Meter readout on battery shows fully charged yet the lcd screen shows only one bar.
After 3 weeks watching every video known to man on this subject, I’ve fixed it.
Press all 3 buttons on the lcd screen all at once and hold for a few seconds.
Eventually the screen will show either the number 45, 36 or 24. These readings should match the voltage of the battery. Mine was showing 45 when in fact it needed to read 36 to match the 36 volt battery. Just press up or down to show 36, release all buttons together and as long as it’s still reading 36, switch off at the battery, wait a few seconds, switch back on and it will now show full charge at the display. I’m absolutely euphoric to have this sorted, something no professional could tell me, not even Wisper tech dept could tell me. Good luck, and please let me know if this helped. Art