Make sure the battery has been fully charged (the battery needs to be charged for at least 8 hours the first time it is used, after this first charge the battery can be fully charged in 3 hours).
Make sure the battery is well connected. The compartment for the battery is located in the column of the lamp. It is protected by a metal cover. The metal cover is connected by magnets; pull the metal cover to remove it. Inside the case there is a cable with a silicone plug. The battery & TYPE C-USB plug must be fully connected, the silicone plug should overlap the battery to guarantee a watertight sealing.