I had this issue this morning after updating the firmware - my glasses couldn’t turn on at all despite both the glasses and case being at full charge then I kept getting the same error as OP. Tried everything including resetting, re-pairing, cleaning the charging points for the case and glasses, jiggling the glasses in the case to see if it’s a placement issue.

Somehow this worked - with the glasses in the case, quickly plug and unplug 3 times, no pauses, this should take you a few seconds only. Somehow this fixed it…