I’ll note that I can access my library and have been able to access it through all of the recent updates.

We can’t provide much help with the information you’ve given about your system and library.

You’re probably going about it the wrong way. 

However, that’s probably not your fault as the first two options in the desktop app to ‘share’ your library no longer work and will never work again. Sonos have elected to leave them there to confuse people.

 
The only method that works is to create a proper shared folder for where your music library resides and point the app to that. 

The other possibility is you have an old NAS drive which may not support SMB2 protocols. Support for this was also dropped at the same time the new App and speaker firmware was released. 

Thanks for that.   It’s been a long haul.   Think I’ll use iBroadcast.

 Where is your music library?

My Library is now with iBroadcast and it’s working fine.   A good solution to the library problem.   If Sonos ever resolves the issue I might switch back but for the present the iBroadcast option is really good.