The PLAY:1 does not have a microphone, and can not be used as an ‘Alexa enabled’ device. 

That being said, I do control a PLAY:1 using an echo dot, using Alexa voice commands.

Thanks
Yes I’m aware that there is no mic in the Play:1
But do have plenty of Alexa devices here to perform the voice control part
Although the phone running the Alexa app could also do that 
 
If only I could the Alexa app to detect the Sonos speaker ?

Process I’m using 
https://photos.app.goo.gl/ANFDfWsM1Z5tmfvG6

This is the process you should be using:

https://support.sonos.com/en-us/article/set-up-an-amazon-alexa-device-to-control-sonos

If it’s not discovering your device during that, I’d recommend that you call Sonos Support directly to discuss it.

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

Thanks 
Yes, that linked page is the process I’m trying 

I’ll give them a call later this week , see if they can help

If it gets fixed, I’ll report back here what the issue was

Called support …..

Feeling a little bit silly ….

Supp: 1st question : “Despite fact its reporting unable to find device, have you tried asking Alexa to play via that device ?”
Me : “Not sure, thought I had !”
Supp: “Give it a try ….“
Me :  “Ah - That seems to be working OK”


So just because it (Alexa)  says “Unable to find a device” 
Don’t necessarily believe it  - Actually try a voice command