Factory resets rarely do anything other than hiding, sometimes, the issue. What I suspect you’re experiencing, because you have this device wired, is one of two problems. The first would be a duplicate IP address issue, which can occur whether a device is wired or wireless, it’s an issue with the Sonos getting data from the router consistently. Try unplugging your Sonos from power, then reboot your router. Give the router a couple of minutes to come back up before plugging back in your Sonos. 

The other option is a bad Ethernet cable/connection, which may be harder to deal with. I’d start by trying to reseat the cable at both the router, and the Sonos device. Then I’d try a different cable, and if possible, a different cable port on the router, just in case the port itself has failed. Unfortunately, I don’t think there is more than one port on the Sonos, on the other hand, I don’t recall a case where the Sonos Ethernet has failed, but it is merely a part, and any part can fail.

So if neither suggestion works, I would submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Airgetlam

i did exactly what you said to do.  My speaker played for 1 minute and dropped out.

i checked the Ethernet cable and it has no issues.  I have a tester as I made all of the cables for my house.

i changed ports on router.  Still drops out.

i tried a different speaker.  Same issue. 
I have no issues with any other device in my house, or garage.

the speaker situation that i have had continuous problems with is 100 feet away from the router, in my garage.  I pulled cat 5 out to my garage to have a connection out there.

Could it be a setting?  Do I need to set the garage speaker as a group?

I am at a loss.  Been battling this issue for 2 years now.  No one seems to be able to remedy the situation.  I can’t figure out why it’s such a problem as it’s just a speaker plugged directly into a router.

pretty disappointed as it took a lot of work to actually get the Ethernet connection into the garage.

i have plugged other devices into the cable and had no issues.  Only Sonos issues…….

What did Sonos support say?

Do you have any other Sonos speakers? If so, how/where are they connected? 

I have 3 Sonos One and one play bar.  They are all running off of WiFi.  The situation that causes me trouble is the hard wired speaker in my garage.  Never got it to work properly.  I had another router in garage working as an extender.  Tried running speaker off of WiFi from that router.  Never worked.  Tried wiring it direct from that router.  Never worked.  So I unplugged secondary router and plugged speaker directly into Ethernet cable.  Still only works when it wants to.  Pretty frustrating to say the least.

i have tested Ethernet cable 5 times and it checks out.  I have also plugged a computer directly into cable and had zero issues.