Have you tried a different wall plug?

They may have failed completely, possibly due to power surges. I’d suggest a call to Sonos Support to discuss it.

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.

They’d likely be best at figuring out what the issue is. 

Not that it helps you a bunch, but my two PLAY:3s are working fine…

Have you recently updated the system? Recently there was another similar post. That failure seemed to follow an update. This was not proven. PLAY:3’s are old enough that we might start to see the hardware failure rate creeping up, but while possible (Mother Nature is never fair) it seems unusual that your two units would fail at exactly the same time.

I suggest submitting a diagnostic and discussing this with SONOS phone support. If they are becoming aware of a developing issue, your observation can be a data point. Don’t post the confirmation number here.

Yes, as Airgetlam suggested there could have been a local, destructive transient.

In the past I too have said "my Play 3s are fine"  but I recently powered them on (usually off as they are a room that is usualy unused for weeks or more at a time) and one didn't boot normally. I power cycled it to try again and it came up, paired with the other and worked for my listening session. But I noticed the LED was only about half  brightness  compared to what I expected and the other 3's light.

I'm expecting to see a failure in my future, but given the @ 20 years lifetime so far that isn't a major disappointment. 

One key thing here, given our power system, is a high-quality surge suppressor or UPS on everything more expensive than my bedside alarm clock. I recommend the better quality Trip-Lite ones as they have served me well for many years.

On many of the older models the front panel LED’s dim over time, enough that they are only visible in a dark room or not visible at all. With a network connected, the network jack LED’s should be active.

Thank you and I will be contacting Sonos Support to see if there is a solution. Funny thing is I have another Play 3 on the system that is working just fine. Appreciate everyone’s time and responses!

Out of curiosity: Were all of your units manufactured in the same month? The first characters in the serial number indicates the month. For example 2501 indicates January of 2025. Same date may indicate (not prove) “same batch”. Each batch has its individual series of failure clocks and vulnerabilities. The detail about this failure that bugs me a bit is that the two units seem to have failed within minutes of each other. This suggests a local contribution to the failure. This could be a voltage transient, temperature, static electricity discharge, water, insect invasion, or whatever else we can imagine — such as an update gone bad.