Older Sonos gear does not do Bluetooth for set up. If you do not succeed in setting up the system via WiFi, a network cable is a good idea. Are you using the Sonos S1 controller? Because if your system hasn’t been used for give years it’s software predate the S1/S2 split.
By the way. There is no “2nd gen” Sonos system, just some speakers marked Gen 2.
What speakers do you have?
Did you have a Bridge or Boost connected to your router?
What app are you using? S1 or the new S2 app? If it’s the S2 app you will/may need to get that Ethernet cable since there have been quite a few updates in five years, so that you can update your speakers.
Even S1 compatible speakers have had updates over the past five years.
For kit that old you almost certainly can’t update in a single jump. Speak to Sonos support and they should be able to provide some interim update steps to take from your old to the current version.
I got this resolved with a knowledgeable friend. It involved downgrading the app to S1 and a long process of upgrading all the spreakers, some of which repeatedly failed in the upgrade. They were able to ultimately work it out, everything is working now, and the effort w2as definitely worth it---the turntable is projecting with good sound all over the house. Thanks for the responses.