@Nissesjoman 

Thanks for reaching out. I understand that you've just set up your Deco Mesh system in Router mode and connected your Synology NAS (via Ethernet cable) to the main Deco unit, but the NAS does not appear in the device list in the Deco app. You also mentioned you haven't used the NAS in a few years and cannot access it by any other means.

Here are some steps to help troubleshoot why your NAS is not showing up in the Deco app:

1. Wait and Refresh:
• After launching the Deco app, please wait a few minutes to allow all connected devices to be detected and displayed.

2. Reboot the Main Deco:
• Try rebooting your main Deco unit by unplugging it from power, waiting a few seconds, and plugging it back in.

3. Update the Deco App:
• Make sure you are using the latest version of the Deco app from Google Play or the App Store.

4. Check Network Configuration:
• Ensure there are no other routers broadcasting the same Wi-Fi network name (SSID) as your Deco system, as this can cause device detection issues.
• Confirm that your NAS is set to obtain an IP address automatically (DHCP) rather than using a static IP. If your NAS has a static IP from a previous network, it may not be compatible with your current Deco network settings.

5. Reboot the Entire Deco System:
• Power cycle all Deco units in your network to refresh device connections.

6. Additional Tips for Your NAS:
• Since your NAS has not been used in a while, check its physical connections and ensure it powers on properly.
• If possible, connect your NAS directly to a PC with an Ethernet cable to see if it can be accessed or detected outside the Deco network. This can help determine if the issue is with the NAS itself or the Deco network.

If you have tried all the above steps and your NAS still does not appear in the Deco app or cannot be accessed, please contact TP-Link support. When you do, provide details about the troubleshooting steps you've already taken.

Let us know if you need further assistance!

  @Nissesjoman 

That shouldn't wipe the drives on the NAS yes? 

  @Nissesjoman 

Hi, can I have the model number as well as the firmware version of your Deco?

Have you ever set a static IP address on the Synology NAS?

Wait for your reply.

Best regards.

  @Nissesjoman 

Hi, thank you very much for the update.

It is suggested to update Deco M5 to the latest 1.9.1 version:

Deco M5_1.9.1 Build 20250909

It is suggested to use a dynamic IP for the Synology NAS and if you want to have a fixed IP, you can try to configure "Address Reservation"

How to configure Address Reservation on a Deco

Thanks a lot.

Best regards.