Is the Amp grouped with the Playbar or is it set up as surrounds with the Playbar? How exactly are you streaming Spotify to the Playbar?

Yes they are grouped together like you said, set up as surround (see screenshot). 

In the Spotify app there's an option to choose a device to play to and you just choose the group. 

Make sure the Music Playback setting is set to FULL under the Surround Audio settings for the Playbar.

FYI… The Amp is set up as surrounds which is completely different than “grouping” a speaker.

Well I guess maybe I've mixed it up with Alex's grouping terminology. Music is already set to full. See screenshot

I didn't really change anything so I'm unsure as to what would have caused it to stop working

Try removing the Amp as surrounds from the Playbar and re-adding it.

Lol I never set it up so I'm a little worried. Is it as easy as "remove surrounds" and then just add? 

Yes. If you have Trueplay tuning saved, this will have to be redone too.

Hmmm yeah that was easy. But it didn't work sadly. Music plays just fine through the playbar but nothing through these ceiling speakers still

If you have already tried rebooting the Playbar, Amp, and router, and checked the speaker wire connections, you should probably contact Sonos Support.

Just finished debugging the most recent app update on my system.

Speakers would only work in 3/4 rooms after the most recent app update. I did the usual power cycle, reset, update all apps, reinstall everything but still only (any) ¾ rooms function. Attempt number two,  I switched from Spotify to Apple, updated mesh firmware and gave Sonos high priority. Re-installed Spotify to compare Apple and Spotify audio quality. Instantly noticed Spotify was lacking. Then noticed the rear speakers and sub were not working. Back to whack-a-mole speakers, any 3/4 rooms work. Returned to Apple, turned on one room at a time and it’s working again. 
 

The issue is the latest Sonos app update has problems with current and previous Spotify app. It had been working flawlessly since the last debug effort after the previous Sonos app update. 

After deleting my Spotify account, Apple Music worked for a while. I tried to play the tv in four rooms and the issue came back, only 1 or ¾ rooms work. Now, the same issue occurs with Apple music. There goes the rest of my weekend, again.