Hi  @zauberertz 

Please check the points below and see if it helps:
    1. Ensure the EAP is hardwired to the router via an Ethernet LAN cable, use a standard CAT5 above cable for the connection. Usually, we can see a corresponding LED light up on the Router.
    2. Test the EAP's SSID with other wireless clients, and eliminate the issue is from a specific client.
    3. Check the IP information on the wireless clients. To access the Internet, the clients need to get Default Gateway (Router) and DNS Server from your network through the EAP.
    4. Unplug the EAP, and connect a PC instead to the Router with the same Ethernet cable, check the IP info obtained on the PC and confirm it can get internet access.
    5. Reset the EAP: with the EAP powered on, use a pin to press and hold the reset hole for about 8 seconds until the LED flashes green-red-yellow to factory default settings.
    6. Repeat steps 1)-4) if you still get no Internet access from the EAP, this is a detailed FAQ for more troubleshooting tips: What to do if your client cannot obtain an IP address after connecting to the EAP's Wi-Fi
If the issue still persists, please update with the result of the above troubleshooting steps.