What was at the other end of your ‘active Ethernet connection’? Was the speaker connected directly to the router, or was this some sort of mesh Wi-Fi extender puck of some type? What type of router do you have? Do you have any other Sonos devices wired, or do they all hang off you Wi-Fi?

The speaker is connected to a switch in my closet which is connected to our apartment community router.  One of the ports on my switch is a Philips Hue hub, which is online and working well - connecting to the internet, my iPhone, etc.  I have tested connectivity to the port my Sonos is connected to, and it is active as well.  (Gets IP address, internet is available, etc.)

This is our only Sonos device.

Sonos needs a direct connection to the internet during initial setup. Often an update is part of the setup. Going through a switch and using a community router is not recommended. Sometimes a reboot of the router is required which in your case appears not an option you have.

Could I use my iPhone hotspot in this case?  That would give me a direct connection to the internet.

As long as you’re using another device to run the controller on. The controller can not be run on the same device as is providing the hotspot. 

Thanks. Will respond with results.