Switch XMG1915-EP

Hi @Cumbria,

Welcome to the Zyxel Community!

To better identify the root cause and the exact step where registration is failing, could you please share more details along with screenshots or a short video if possible? This will help us pinpoint the problem effectively.

Additionally, please confirm and share:

• Is the switch failing to register with NCC, or is it failing to come online?
• Does the switch have an IP address assigned?
• What is your network topology like? How are the three switches connected?

In the meantime, please take a look at these FAQs which often resolve registration and offline issues :

• [NEBULA] How to register Nebula devices on Nebula Control Center? — Zyxel Community
• Why I cannot add my device to Nebula? — Zyxel Community
• Zyxel Nebula Switch Troubleshooting Guide — Zyxel Community

Once we have more information regarding your environment and the specific error information, we will be able to provide more targeted assistance.