Sonos Port is not working properly with turntable

Not sure if this might help, but if the Arc, Sub and Eras are set up as a surround sound system, my first suggestion would be to reboot your router and then to check that Autoplay under the Line-In settings is pointing to your surround system.

Dear lain69, thanks for your answer! I did it like you suggested and afterwards it just worked with both Era's in Surround Setting/Music playback in “ambiente” mode, but sound was not really good. After changing to “complete” only one Era played music. I tried out several settings and played around a bit, but nothing really helped. I have to say, I just always used the one side of my Pink Floyd record and then that's really strange (at least for me). I turned the record around. And what should I say, the sound of Arc and Era's were fine. Unbelivable! Could it be that the pre-amp of the Pro-Ject T1 is the problem??? It is also really new. Do you have an idea?

Check silly things, such as RCA plugs not fully seated in the jack.

As Buzz says, check the RCA plugs are seated. Also worth checking that the switch on the Project phono amp is set firmly to line out,  switch back and forth a couple of times. The fact that you’re having problems with the surround setup does tend to suggest that any issues are Sonos side rather than the Project, though loose connections are always a possibility.

Thanks buzz and lain59! The RCA plugs were fixed in the turntable as well as in the port. The Pro-Ject T1 doesn't have a switch so you can only use it with pre-amp. At the moment everything works ok, but it did a few days before. It seems to be a problem that occurs randomly from time to time. So I'm wondering, is it the T1's pre-amp or a general Sonos App or Sonos Port problem? I don't know how else I could narrow it down...?

Sorry, I have to correct mmyself, the Pro-Ject T1 has a switch and it was set to LINE OUT correctly.

Fault finding at present is made hard by the unreliability of both the App and Sonos firmware, random faults all the more difficult. The Phono Pre Amp on the Project T1 is a pretty straight-forward affair, most problems I’ve had with amps over the years usually express themselves as weird buzzing but they can go wrong. Random problems do tend to be part of the stability issues with Sonos at present, fingers crossed yours settles down. 

If problems persist then submitting a diagnostics report soon after it’s occurred then contacting Sonos Support is probably best.