My sonos was working fine with upgraded sonos firmware in sonos play:1 system but it stopped working sometime back.

Here are the things i tried to fix it:

1. Reset the sonos play:1
   • Turn of power supply → press play button & volume up together (> & +)→ Turn on power supply → hold until it reaches permanent green light.
2. Reset the sonos S2 app.
   • Go to profile → App Prefrences → Reset App
3. Set up the sonos again after above 2 options using Ethernet Cable.
4. Setup done sucessfully over Ethernet but when Enabled the Wireless Network in App, it didn’t ask for credentials.
5. Also when tried to locate the Sonos Product in App it wasn’t able to find it.

6. Went through following page which didn’t help much but atleast one comment caught my eyes “the WiFi network though needs to be 802.11b/g/n compatible with security mode WPA-2 personal and the Sonos mobile controller device needs to meet these system requirements…”

7. Also few comments suggested to downgrade Play:1 and try with S1 OS and APP.

Now have to try these things, so did below:

1. Downgrading part - it’s not very clear and had to struggle to do this, but let me put the down the steps.
   1. Reset the sonos play:1 (same as mentioned earlier)
   2. Reset the sonos app (same as mentioned earlier)
   3. In S2 App - go to Settings → Visit Help Center → Legacy Apps (Sonos S1 App) → Downgrade Product to S1 → Follow the setup process to downgrade
   4. Voila got it sucessfully downgraded. 
2. Installed sonos S1 app
3. Did the required setup while sonos was connected to Ethernet and was able to sucessfully setup.
4. Now time to setup wireless in Play:1
   1. Went to settings → system → network → wireless  setup
   2. Selected the wifi and entered the password → “Password incorrect”
   3. Tried resetting the password of wifi, didn’t work at all. 
   4. Tried following all the steps again (reset play:1, app, setup then wireless setup) but it again didn’t work.
5. Now comes the very important part:
   1. Went to my home router settings and validaed it was in 802.11b/g/n compatible mode.
   2. One thing my route caught the eye was Channel, it was not in Auto selected mode, it was in Channel 44 (I have seen somewhere Sonos had three Channel 1, 6, 11) → So modified the router settings for Channel to Auto → Restarted the router.
   3. Followed all the steps again to be ensure it works now → Reset play:1 → Reset app → Setup over Ethernet →  Wireless Setup → This time it connected with the password without any issue.

Now i’m going to always refer these steps as and when i face this issue, maybe it will be of some help to whoever is facing issues with their old sonos products.