Everything under the Manage tab is greyed out. Why?

It make no sense that Sonos would purposefully do this, rather than being forced to do it because of limiting factors in the MacOS. There is absolutely no benefit to Sonos when its users have to upgrade their Apple hardware. On the other hand, Apple and the term "forced obsolescence" have been almost synonymous for years, and it is no secret that Apple builds new features into the latest OS build that can only be accessed if the old OS versions are abandoned, often far more prematurely than is necessary.

And the other option is to use another device to do those things that can't be done on the offending computer. Say, a newer iPhone, or iPad, or Android device, or some other laptop/PC. Even if your data is on the "I can't upgrade this" device, you can use Sonos' controller on any device that is connected to the Sonos Speakers to make changes.

And are there any words on here that can produce such a feeling of dread as "I'm an IT guy"? Oh yes...."I am a network engineer".
Please note that it is your Apple equipment you have to upgrade, not your Sonos gear.

And are there any words on here that can produce such a feeling of dread as "I'm an IT guy"? Oh yes...."I am a network engineer".
"There's nothing wrong with my network" must come close.

And are there any words on here that can produce such a feeling of dread as "I'm an IT guy"? Oh yes...."I am a network engineer".
Please note that it is your Apple equipment you have to upgrade, not your Sonos gear.

Yes, there is something worse...those who feel incompetent and try and make themselves look good by tearing others down. Looks like to me that someone needs to go read RULES OF NETIQUETTE. LOL Have fun "boys".

"it works at my desk/on my computer" is a common one in game development.

"it works at my desk/on my computer" is a common one in game development.

Yes, the Sonos equivalent is "TuneIn/Spotify/Pandora/etc. plays fine on my phone."