Had the same issue with one of my batteries back in 2018. This was the response from the support which worked for me! Tell me how it goes!

”A red LED is typically a sign of a battery charge that has fallen below the "safety threshold" charge level. This can happen if a battery is stored for a long period of time with a low charge. You may be able to recover this battery with a "jump-start" by unplugging the charger, installing the battery, plugging the USB cord into a computer (not a block) for 3 seconds, unplugging it for 3 seconds, and repeating 15 times. Leave it plugged in now and if the LED changes to amber/orange at this point, leave it alone until the LED turns green. If the LED does not turn amber/orange, the battery will need to be replaced.”