Has anyone had success with the S1 app?

There are many thousands of users still running S1 devices purchased in 2005 — much older than your PLAY:5.

Your first steps should be rebooting the PLAY:5 and restarting the controller. Refrain from PLAY:5 Factory Reset before working with SONOS phone support.

Is your PLAY:5 wired to the network or wireless? Are there any other SONOS units in the system? Have the PLAY:5 and controller been recently updated?

Also, make sure your PLAY:5 is actually running S1. I have a pair of PLAY:5s which are gen 2 and are running S2, not S1. 
 

Sometimes, it helps, at least initially, to connect the speakers to the router with an Ethernet cable, which mostly removes wifi interference as an issue, which can be dealt with afterwards. 

Did you just recently purchase the PLAY:5(Gen 1)(s)? It could be they have not been updated in a long time and will not update without assistance from Sonos Support (Sonos Support). You might give them a call.

Thanks for the help everyone, much appreciated. I have owned these since 2014ish and they’ve been in storage for the last 5 years so it sounds like I need Sonos support to try and get them updated. I can’t get the S1 app to do anything on my Pixel 8 though and I’m not sure why it won’t work. Just blank screens like something is loading and error messages when I try to do something. I hope I can get it figured out as these produce really nice sound and I’d hate for them to become paperweights. I’ll call Sonos support and see if they can get them working.

To answer your questions, the one I am trying to set up is a Gen 2. It is connected to the network via ethernet cable. I have one other Play 5, a Gen 1, that I haven’t had any luck with either. I’ll keep trying.

5 years in storage definitely means the firmware is too out of date.  Sonos support needs to push an update directly to the units before they can be used with the current S1 app.