Hi @TPComputer 

To better understand the issue, please share with us the following info:

1. a screenshot of the Device page so we could know what kind of Omada SDN EAP devices you are using;

2. A screenshot of the error message page;

3. A screenshot of the SSID config page.

4. What kind of controller you are using? (you choose both cloud-based controller and software controller for this thread).

  @Vincent-TP 

  @TPComputer 

Hi Vincent,

here is my Devices Page

And here is the SSID Page. 
I create a new WLAN group and copy all SSIDs from the default group. When I do this, the message "The SSID "TPC 5G, TPC 5G Terasse" is illegal and will be deleted."  appears. 

I'm using the cloud-based and the software-based controller for testing. The error occurs with both.
Thank you for your support

Thomas