This is almost certainly not a power issue but a network connection issue.  If they are regularly disappearing after an hour then the first thing I would do is to check that the IP address lease time on your router is not set to one hour.  I would also reserve IP addresses in the router for your Sonos devices.  

Otherwise, please tell us more about your network setup: make and model of router, whether a mesh, extenders etc.

I’ve got an “orbi ax1800 wifi 6 dual-band mesh router” no extenders. router is about 5-10m away from the living room where the speaker set up is. 

Will look into the IP address lease time etc.

If it isn't the IP addresses the chances are that it is something to do with your WiFi switching bands or speakers connecting to different mesh nodes.

Can you please confirm that your Orbi mesh contains a router and does not work in conjunction with another router?

If that is the case then please try the following experiment.  Separate the stereo pair and connect one of the Sonos One speakers by Ethernet to the primary Orbi device / router.

Power off and on the other speakers. Check that in About my System all speakers have WM=0.  See if that solves the problem then we can discuss your options. 

(Note: if it works like this then this tells us that it isn't an IP addressing problem, amongst other things.)

I turned off the 2.4ghz on the router settings (5ghz remaining only) and allocated sonos its on IP address and it hasnt dropped out since so here’s hoping that was the solution.

I’d be tempted to turn back on 2.4Ghz. My suspicion is the allocation of the IP addresses resolved the issue.

I agree with Bruce that there are probably better options than losing your 2.4GHz band.  (Any thoughts you may have that 2.4GHz is somehow inferior to 5GHz should be dismissed.)  For example, if the system has a ‘band steering’ option enabled, you may find that disabling that is sufficient.

It may just be your phone that was switching bands, not the speakers.

But if your system continues to work well (Sonos and everything else using your network) then there is a case for not changing anything.

Any further problems, please post back

Thanks for the replies. I've unplugged the arc to wall hang it now and now only one speaker will connect back to the app. This is getting frustrating now!

I turned 2.4ghz back on... factory reset the arc and speakers and it says "add arc" I follow the process and it says it may not show up in system so power off and on and it will show up. I do that and nothing there... same with my sub and other speaker. 

It feels like they're connected but to another network or system or whatever the right terminology is... is that possible if so how do I access that... 

Arc? Where did that come from? Are your speakers and Sub part of a Sonos HT system? If so, that is a pretty significant omission in the info you provided.

Edit. And factory resetting the Arc and Ones was a mistake.

You will indeed get frustrated if you take random actions that make the situation worse.

Arc wasn't the issue at the time. Haha. Was trying anything to sort it. Looks like arc can detect network but seems to be blocked or something but my router settings don't have any blocked 

The Ones and Sub connect in a totally different way when acting as part of a HT system. It is a completely different problem.

Right.  Well I didn't know that sorry mate.  Any ideas on my router settings that might be blocking the arc?

OK.  This is fairly new to you so why would you know?

So let’s take stock.  You have an Orbi mesh system.  Does your network also include a router, e.g. one supplied by your ISP?  Or is the Orbi all there is?

Do you have any other Sonos devices besides the Arc, two Ones (as surrounds) and Sub?

Has this worked ion the past and stopped working, or is this a new setup?

Do you have any Sonos device(s) connected to the network by Ethernet or is everything wireless?  If needed as a temporary experiment, would it be possible to connect the Arc to your router by Ethenet?

I am sure this problem can be resolved - we just need to work methodically and slowly through it.