Does this turntable have a built in preamp? If so, you’d need to turn it on, usually marked as ‘line’, rather than ‘phono’. If not, you’d need to purchase a preamp, and place it between the turntable and the Sonos. 

Hi, Thanks Bruce. The turntable does have output select as ‘line’ or phono’ and had this switched to ‘phono’??   

Line is the amplified signal. Have you tried it?

Here is a good reference between Phono and Line levels. All Sonos line-ins are looking for line level data. You’d want that switch set to ‘line’, as 106rallye suggests, and I indicated in my first response. 

Hi @Murls 

Assuming as others have suggested your turn table is pre-amped (or using and outboard pre-amp) and line-in is selected; that part of your connection to the Connect:AMP is taken care of.  However, when you say you have two Sonos One’s connected to the Connect:Amp that is an inaccurate statement.  Hopefully, you mean you have the Sonos’s One’s as a stereo pair named as a room and have set them to autoplay as outlined here.