@SimonFa 

Here are some troubleshooting steps to help you access the web interface:

1) Make sure your device is connected to the Deco network • Verify that your PC or phone is connected to the Deco network (via Wi-Fi or Ethernet). The web interface is only accessible when you're connected to the Deco's network.

2) Disable any VPN applications • If you have any VPN applications running on your PC or phone, please disable them as VPN connections might prevent local network access.

3) Try using the LAN IP address directly • Instead of http://tplinkdeco.net, try accessing the web interface using the LAN IP address of the main Deco. The default address is usually http://192.168.68.1. Enter this directly in your browser's address bar.

4) Try https instead of http • Some browsers may require a secure connection. Try accessing https://tplinkdeco.net instead of http://tplinkdeco.net.

If you've recently changed your TP-Link ID password, make sure to login to your Deco app with the new password first before attempting to access the web interface.

If you're still unable to access the web interface after trying these steps please reply back to this post.

Thanks