@Hahniv 

The Deco M9 will by default set its LAN as 192.168.68.x. In your case, you are running your network as 192.168.1.x. 

If you have set IP addresses, set them to .68 or your network will no longer function.

I think that is the reason why when there are reboots the Deco will revert to 192.168.68.x.

@Tony Within the app you can select your LAN protocol which mine is set to 192.168.1.xx.  My network was setup WAY before the Deco came into the picture.  Changing to thier default would be a monumental task.  It shouldn't have to happen.  When the system reboots it should go to the protocol that it is assigned within the app.  Yes I beleive that it is going to the default which is causing the problem.  The question is how do I make it go to the app assigned protocol without endless reboots.  If you couldn't have a different protocol it wouldn't be an option in the app.  Actually every router on the planet has the ability to setup your own LAN address.

@Hahniv 

I would verify if that may be happening. When tested on our end the assigned LAN IP stood the same.

You mentioned earlier is rebooting the modem while the Deco is on can being back the network. If the issue happens look at the LED light on the main Deco. If that is red, then it is no longer getting an internet connection. You could try swapping the Deco nodes to see if the issue is with the LAN port on the Deco, swap the Ethernet cable, and also (if possible) look at the modem system logs to see if there is an issue with the internet signal.

@Tony The LED on the main Deco is green.  Satellite Decos are red.  I"m not sure if I reserved the address on the satellite Decos or even if you can.  Back when I first got the system we went through all the trouble shooting you have suggested.  I've changed main Decos, I have changed ethernet cables.  Not sure how to get into the modem system logs but I can connect directlly to the modem on my laptop and there are no issues with the internet.  Nothing changes with the internet once the system is back up and running after screwing around with it for a long time.  I know I'm in troublle and judge when the sytem is backup when the Wemo home automation light switches which have their IP address reserved start blinking which happens when there is a wifi error.   Once they stop blinking I know I'm good to go.  My iPad had it's IP reserved so of course I couldn't get into the app when the system was down.  I removed the reservation and was able to log in, I checked the LAN IP setting which it was showing the correct 192.168.1.xx so the app had the right IP for some reason that's not getting to the main Delco.  

When it's up and running it's great.  My electical utility company is pretty good, I don't have many instances with the power going down.  When I first reported this problem it was when I was first setting the system up.  After much back and forth no one could figure anything out and we just started doing the same thing over again which it's a nightmare everytime the system is messed with.  Just happened again because of multiple power outages due to the installation of solar panel necessitating the shut down of the house several times.  A nightmare ensued each time.  My electrical system will be more stable now because along with solar panels I also have a battery powerwall.  I may have 1 more power shutdown ahead as the utility comapny commissions the system hopefully this week.

I don't understand why the router doesn't startup like every other router I've owned .  This replaced an AmpliFi HD mesh system which developed a problem with the router (it would not run faster than 100 mbs) which because of a weird company policy, if you buy a kit you can't replace 1 component, I decided to go in a different direction.  I still have it as a backup (just won't go faster than 100 mbs).  I fired it up just for gins, it came up as it always did, no issues with LAN IP or all the IP reservations.  So I think you can rule out any problems with the Modem which is an Arris SB6190 if that makes a difference.

@Hahniv 

If the satellite units are becoming red then it is no longer getting an IP from the main unit. If you already tried moving the satellite units closer and swapping the Deco units then it would be best to reach out to our support at that point.

@Tony Is there some sort of log file on the Deco to see exactly what it is doing?

@Hahniv 

With the latest firmware of the M9 v1 that should have web access.

Here is how you can view the logs:

https://www.tp-link.com/us/support/faq/2641/