Not really enough information to give you a comfortable answer, but a guess might be bad cables between your amplifier and the CONNECT, or possibly the need to re-seat them. 

The key piece of information here is that the CONNECT is not sensing an input at all. You could try just connecting the cassette deck directly, and see if that works, as it could be an issue with the Amp, or the cables. Or, it could be a failure in the line in circuitry on the CONNECT, in which case I would recommend that you submit a system diagnostic , and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis.

@Airgetlam - Thanks for the response Bruce. I will check the cables again however have re-seated the cables once and this set up was working not that long ago. Components do fail however so I’ll try what you suggest regarding a direct connection and see where we go. Cheers  Howard

You did say you had reseated them, which I glossed over in my initial reading of your post, but it’s worth trying a different set of cables. But it may be an internal issue, which I think the diagnostic might pick up. Good luck. 

However, if it isn’t an rare internal Sonos issue, some additional information about how and where the cables are connected at both ends would certainly be helpful to anyone hoping to help figure this out. Which make and model of the amplifier, along to a link to an online manual wouldn’t be remiss, either. Especially if the amplifier is programmable, or can have firmware updated in it. 

Hiya, its an old Pioneer Amp, model SA-420, pretty Lo -Fi and certainly no software in there! :) I only use it occasionally to play old stuff that’s still on album and tape!

I have the Connect wired to the aux headphone output on the amp, which I assume is piggy backed somehow to the amp’s main headphone socket, which I know works through headphones, so I have assumed for now that there is also a signal going to the Connect. At the connect end, I have this wired to the ‘Analogue In’ port. I’m not sure how the connect knows it has an input prior to, say, playing a tape or an album, unless there is a quiescent signal that it picks up. Haven’t tried a direct device connection yet and plan to do that shortly. Thanks.

Does that headphone output on the back respond to the volume knob on the front, or is a fixed output?

For those of you playing along at home, my reference is here .

Its a fixed output.

Well, that’s a blessing, at least. Doesn’t solve the problem, but removes one possibility from the thought process. 

I need to also check if there is an output from the Aux headphone channel. That’s all I can think of other than something wrong with the connect.

Ok, have just gone direct from my turntable to the Connect with a new cable set and still there is no recognition that there is a line in connection present. The issue has to be with the connect?

Seems so, given all the testing you’ve done. That’s why submitting the diagnostic, and contacting Sonos is so important. There could be something I’ve missed, and there could be something showing up in the diagnostic. 

Ok, will do that. Thanks for your help to date Bruce. I’ll let you know what the outcome is.