If you’ve been riding the bike and the battery is hot when you start a charge, the charger may not recognise it as empty ie will show a solid green light. You will need to allow the battery to cool before charging. Much like a lithium power tool battery, when it’s been used and still warm, the smart charger will not charge it to prevent internal damage to the battery. Allow the battery to cool (approx 30-45 minutes) and connect the charger. It will show the flashing red light to indicate charging. Once the battery is charged, turn it off at the power point to prevent overcharging/overheating.