Hello @Erky32 ,

The Powerline LED is usually represented by a 'House' icon on your device and shows the status of the powerline network connection.

• Steady ON: This means the device has established a stable powerline connection with another adapter/extender.
• Blinking: This typically means the device is in the process of pairing, or there is intermittent connectivity between the adapters. If the LED keeps blinking and does not turn solid, it may indicate that the devices are not properly paired or are experiencing connection issues.

Regarding your 3-phase electrical setup: Powerline adapters work best when they are on the same electrical phase. The Powerline LED does not directly indicate whether the devices are on the same phase, but if the LED is steady ON, it means a connection has been established. If it is blinking or off, the connection is weak or not present, which can happen if the adapters are on different phases or if there is interference.

If you see a red Powerline LED, it means the signal strength is poor. You can try the following troubleshooting steps:
1. Plug the extender directly into a wall socket, not a power strip or surge protector.
2. Keep the extender away from high-power appliances or devices with motors (air conditioners, washing machines, etc.).
3. Move the extender closer to the main powerline adapter.
4. Update the firmware of your Powerline devices.

For more troubleshooting, please refer to:

What can I do if I can't have Internet connection 
How to update the firmware using tpPLC Utility