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Switch off your Play-3.
Leave your other devices (Sonos One/Play-1) working, with one of those devices connected to the router ... this will put your system in Boost Mode and you need to check both your original speakers are viewable in your Sonos Controller App.
When they are working correctly... now cable your Play-3 to the router aswell and carry out the hardware reset procedure as shown in the link below.
Note the LED light on the Play-3 speaker (see other link below). If the LED light gets to a flashing green you can then try adding in your speaker to your existing Sonos Household through the 'Add Player or Sub' setting in the Sonos App.
If this fails again, then it’s best to immediately submit a diagnostic (see last link below) and post it’s reference number here and ask the Sonos Staff to take a look at what’s going on.
Factory resetting a Sonos product
LED Lights on Sonos Products.
Submit System Diagnostics