This issue is commonly known as a "sleeping Sola." It can happen to old and new lights alike.
Why do Solas do sleep?
This sometimes occurs when a Sola light is in storage and hasn't been charged for an extended period of time or the battery has been run all the way down after a dive and was neglected to be charged within adequate time. Our engineers have designed the batteries to hibernate in order to conserve remaining battery life and prevent deep discharge.
*Deep discharge is a term for a battery in a state of unrecoverable and complete depletion.
How to "wake" a Sola:
Plug your charger into the wall and proceed to tap the charger prongs rapidly against the light's charge contacts for 5-10 seconds, the immediately plug the charger all the way in. This surge of power can jolt the circuit, allowing the light to power back up and start taking a charge. This can take a couple tries, so don't give up the first round!
Be aware that the Sola can sometimes take up to 10 seconds to start charging even on a good day, so allow the light some time to begin charging after you've completed the tapping part of the process.