There are a few things you can try to make your WakaWaka work again.
First of all, it is important to check all indicator lights: to see to what extent the WakaWaka is charged, you can push the big button.When you attach a device to the WakaWaka, the blue indicator light should go on. Only then you can be sure the WakaWaka Base is charging your device.
You can try to use another cable/phone. Sometimes the problem is in the cable and not in the WakaWaka.
Try another USB port. You can try to push the big button for at least 10 seconds. This will reset the WakaWaka and after that it should work again.
Fully charge the WakaWaka from the AC grid to give it a power boost- The battery of the WWB5/10 has a capacity of 5000/10000 mAh. Meaning, devices with an equally sized or smaller battery capacity can be fully charged with the WakaWaka Base.