I’ve also deleted and reinstalled my Sonos App. 

You perhaps may have reached a limit in the Sonos App? IIRC, it used to be 10,000 tracks across all playlists in the App, but that’s just something I’ve read here in the community in the past, but it might also be the case that the Spotify music service has its own restrictions too, but I’ve not personally seen those things mentioned previously.

Maybe see if removing a non-essential playlist will cause another to appear in the App in its place, albeit removal of such things is entirely a matter for yourself, but that step may infer some kind of limit has been reached.

To also help check these things, you maybe best to submit a diagnostic report from the App, note it’s reference and then speak with Sonos Support Staff instead, albeit after the holidays - see this link to contact them:

https://support.sonos.com/s/contact

That will not change anything, there is almost no data stored in the app itself.

If you count how many playlists are showing, you will likely find it is a multiple of 100, which means you have hit a size limit in Spotify’s Sonos integration.