@Rafid_Anjum 

What is the current network diagram? 

When all devices get cut off, what is the led status of the Deco M4? In the meantime, with your computer connected to the modem directly, can you access internet? 

Is there any error message if they failed to join Deco's network? With your computer connected to the Deco by wired cable, can you access internet? 

Thanks a lot. 

@Kevin_Z 

Network Diagram:

When all devices get cut off, the led status of the deco m4 still WHITE. In the meantime, my pc which connected via LAN still connected to the deco and the internet on the pc still works!! I can still use the pc on my phone via teamviewer if i turn on mobile data on my phone. So lan port works good as it should !!

Sometimes it showed "Connected,No Internet", Sometimes it shows "Unable To Connect To ɘꙅuoH bɘƚᴎuɒH" or bla bla !!

I've attached the network logs In One Zip:

@Kevin_Z 

While my some wireless devices can't get internet & others can't connect, I've turn on mobile data on my phone and goto TeamViewer to browse my pc and save the network log. At this time failure the internet on my pc which connected via Lan works fine too !! So before restart the deco I've saved the log files !!

Note: Usually this happened almost every night. When I awake from sleep saw the problem.

Log File:

@Rafid_Anjum 

Thanks for your valued reply. 

Try to simplify the network diagram. In other words, please connect your main Deco to the modem only and then connect your clients to this Deco, you can take some time to test its performance. Whether the wifi disconnection issue happens again. 

And do both 2.4GHz and 5GHz have the same issue? 

Besides, you can swap the locations of the Deco units or switch the slave Deco to the main Deco to test its stability.

https://www.tp-link.com/support/faq/2400/

Good day. 

@Kevin_Z 

I have only one deco and its connected to the media converter and all devices are connected to the deco. 

@Rafid_Anjum 

I see, thanks for your reply. 

Is it possible for you to connect the Deco M4 to the modem/internet source directly, bypass the media converter? 

Could you please give us the whole network diagram? And who is your Internet service provider? 

Thanks a lot. 

@Kevin_Z 

It seems strange !! I've notice that at 3:20-3:40 am at night internet stopped working on all devices which are connected via wirelessly. If I restart my phone which one has the deco app installed, all the devices started working again !!!

Deco can't connect directly because the ISP give me optical fiber cable. Media converter convert optical fiber cable signal to cat6 signal.

My ISP is "Infolink Limited Bangladesh"