@gauthamcode 

Hi, did you set Deco X50 before?

If yes, with the "Dynamic IP" connection type, it is plug-and-play once plugged into the network source.

I think you could try to manually reset the Deco X50 once by holding the reset pinhole for 1s, then check whether its LED light could turn to flash blue.

Thank you very much and best regards.

  @gauthamcode 

Hi,  May I know the hardware version of the Deco X50 and could you please leave me a message with the MAC address on the Deco X50?

I don't think it is defective and I remember that the latest patch of Deco X50_V1 with firmware 1.4.0 and above mentioned a new network configuration protocol---TSS (TP-Link Simple Setup) Auto Discovery, which might be related.

Decos are now able to quickly discover nodes that support TSS(TP-Link Simple Setup) whether they are pre-networked in the factory or not. You will then be presented with corresponding prompts from the Deco App to confirm that the nodes should be added to your network – making your network setup and upgrades simpler and easier than ever.

Deco X50 could be connected to Deco M4 When M4 is the main Deco.

Compared with resetting  Deco M4, it is suggested to try the following suggestion:

1. unplug the Ethernet cable between Deco X50 and M4. 

2. check the LED status on the X50, whether blinking red or solid green.

3. if the LED is blinking red, you could reset it again and try to add it wirelessly into the Mesh network of M4.

Wait for your reply and best regards.