@Francoisgs 

Hi

If your home has thick walls, products that extend the signal through Wi-Fi may not perform as well.
1. If the entire building is on the same electrical circuit, it is recommended that you try Deco PX50, which can transmit signals through power lines. But you might need to consider returning the X50 because, while compatible with the PX50, the X50 doesn't support powerline.
For more information about the PX50, please refer to:
https://www.tp-link.com/support/download/deco-px50/
2. Or you could consider connecting the X50 via wire.

It is also recommended that you talk to the shop about the return policy before purchasing Deco PX50.

  @Joseph-TP Thanks a lot for your feedback much appreciated!

Returning my X50 is regrettably out of question as I have them for over a year now. The whole house is under same electrical system , I got a pretty good coverage with my X50 everywhere but one section less open and with pretty thick wall unable proper and strong coverage (now weak and unstable)  in one section. My supplier told me to use X60 as router or X80 but searching found P9 and verify with my supplier who mentioned there will be issue with supply if on 3 phases .

I am surely not IT and want to find the best solution at affordable price ;)

Thanks

Francois

  @Francoisgs 

Here is my recommendation.

1. Get pair of standard TP-Link powerline adapters, such as "TL-PA7017 KIT" or "TL-PA7017P KIT"

2. Place one of them near Main Deco, another - in the area with very weak WiFi. See if they can established connection to each other and their status lights show all is OK

3. Connect powerline adapter that is near Main Deco to Main Deco with Ethernet cable

4. Bring one of your Satellite X50 to where second powerline adapter is, connect it to that adapter with Ethernet cable

If everything done right, Satellite X50 will report Ethernet backhaul.

Check WiFi coverage in that area where second powerline adapter and Satellite Deco X50 now are. If it improved to your liking, leave everything as is and buy single Deco X50 to add to your Deco mesh, in place of one that you "borrowed" for the setup above.

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Make sure you buy powerline adapters from the retailer with the return policy.

The benefits of my recommendations is you don't need to mess with Deco mesh settings, you can keep using Deco X50s you have, and you'll use powerline adapters to check if electric cabling at your place is capable of handling Ethernet traffic. If you don't succeed with one electric outlet, try with another - it'll be much easier to do with powerline adapters than with Deco units.