@David-TP Thanks for responding to my post.

When I was gathering info for the post, I did notice the firmware version was out of date so have updated to the latest version.  Obviously, given the Deco units have been working perfectly for 2 years and 8 months, I don't believe the firmware is the cause of the issue, but it's always good to be on the latest version, providing that doesn't break anything 

I prefer the Deco to assign IP addresses so I'm reluctant to change the config to Access Point and for the BT Smart Hub to act as the router.  Out of interest, why do you think that would "improve" the situation?

If the issue occurs again I will switch the Deco's around and use a different one as the Main Deco as you suggest.

Fingers crossed I haven't had another issue since Friday 18th am, so that's 3 full days now.

Regards.

Paul.

It's been just over a week since the last lot of issues I had with my home network/internect connection.  This morning we lost power to our home for a couple of seconds.  This was caused by a power supply issue at the national grid, so nothing we had control over.  Power was restored almost immediately and everything in the house was working normally except the TP-Link Deco units, which were all showing a solid red light.  Even the BT Smart Hub had powered back up and re-connected to the internet.

A quick Google shows this isn't a new issue and power outages seem to effect the Deco units resulting in the sold red light.

So, a question to TP-Link support:  Why, like the BT Smart Hub, didn't my Deco units startup and continue working after the very short power outage?

This is not the first time we have lost power at home and prior to the issues I've had over the last couple of weeks I have NEVER had to get involved in manually sorting them out.  This suggests something has changed; either the hardware is failing in the units or the firmware has changed and is no longer working properly!

It has taken me ALL MORNING to get these thinks back up and working - that's a complete waste of half a day of my Bank Holiday and I have better things to be doing.

No amount of power cylcing was fixing the issue today - I tried at least 4 times.  At one point they seemed to be back up and working, then 5 minutes later they reported the internet connection had been lost again and all units were showing a solid red light.

I know the BT Smart Hub had an internet connection as I was able to connect directly to it using two different PC's and the internet was working perfectly.  The issues I've been having are therefore specific to the 3 M9 Plus Deco units.

In the end I decided to factory reset each unit and create the network again, switching two of the units so that the Main Deco was a different unit.  This took some time to do, but having added the main deco unit and connected it to the BT Smart Hub, I then added each of the other Deco units, one at a time and everything is now working again.  For how long, who knows!  I no longer have any faith these units will work faultlessly like they have for many years and feel it is just a matter of time before I'm wasting my time trying to get them up and running again.

Although I've wasted half of my Bank Holiday, had this happened on a work day, I would have lost half a day's consultancy rate, which is more than the units cost!

So, I will ask TP-Link support again, in case they didn't see the question above:

Why didn't my Deco units startup and continue working after the very short power outage? 

Also, why are they now failing regularly and requiring manual intervention to resolve?  How do I go about arranging for replacement units under the 3 year warranty, which will expire in December?

Got back home this afternoon only to find the Decos are all showing solid red lights again.  Rebooted and they worked for 5 minutes before sold red lights.

I've had enough of this!  TP-Link really need to explain why this happens to Decos as Googling suggests there are many people having similar issues.  It wouldn't surprise me to learn the hardware had simply failed given they are so close to being out of warranty.

They have been brilliant for 2 years and 8 months, not requiring any intervention, but that has now changed and they simply aren't working any longer.  Why did they work okay for the last week, since the previous issue I had with them and yet today I can't get them to work any longer?  Why has the brief power cut caused this issue?  Why didn't a factory reset resolve any issues caused by the power cut?

Plugged in my old Netgear router and it was up and working within 30 seconds.  The internet connection seems to be stable....  The only reason I replaced the Netgear router was due to the lack of full wifi coverage of my home, plus the need to reboot them on a regular basis due to wifi issues.  The hard wired 1gb network always seemed to be okay.

The Deco units are going back under warranty as they are clearly no longer fit for purpose.

What a waste of my time this has been!

Received a replacement 3 unit Deco M9 Plus system from TP-Link today and configured it without issue in exactly the same way as my previous Deco system.

So far so good, all units working and no internet issues.

Since sending off my previous "broken" Deco units under warranty to TP-Link I was running my network through my two old Netgear routers.  Over the 2 weeks of use I had to reboot the main Netgear router 3 times as "some" devices (not all) suddenly lost internet.  The reboot usually took about a minute (turn off and back on) and everything started working again, so while inconvenient when it happened, it wasn't that much of an issue.  This is how I remember this old equipment working and was the reason I upgraded it to the TP-Link Deco mesh hardware nearly 3 years ago.

At no point was it necessary to reboot the BT Smart Hub, which seems to confirm this isn't loosing the internet connection.

Pleased to be back on the Deco system as the wifi range it much better.

Now I need to re-configure my Tapo smart plugs to connect to the "new" network even though it has the same name as I always use the same SSID, regardless of the hardware being used.

Fingers crossed it continues to work okay, but time will tell......