Some people may have MAC address filtering on their WiFi network. Getting that information is a bit technical and can only be done using an Android device that has Bluetooth LE.
Download a Bluetooth sniffer app like the nRF connect app from google playstore:
When the app is turned on, navigate to the scanner tab. Then press SCAN on the top right corner.
The emberlight closest to the app will have the highest signal strength. In this case it is the red emberlight. Mark it with a star by tapping the BLE icon listed on the right column.
By swiping left you can get to this screen, which shows the BLE MAC ID under “Emberlight”. In this case the starred emberlight’s BLE MAC ID is 80:D2:1D:69:F3:4E.
To calculate the WiFi MAC ID, you'll need to add one to the BLE MAC ID. In this case the starred emberlight’s WiFi MAC ID is 80:D2:1D:69:F3:4F