No search results appear in Sonos app

Searches don't occur on your controller. They occur on your speaker. I'd recommend that you reboot both your speakers, and your router.

If that doesn't work, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this issue, and either post the number here, or contact Sonos Support to discuss it. I tend to suggest the phone folks, they have more tools available, but are only available during business hours. Both the Twitter and Facebook support folks are available 24/7.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

I've got lots of speakers. Do they ALL have to be rebooted?

Diagnostics submitted: 367020602.

Don't know, frankly, it depends on which one is the "hub" of your system. It was just a suggestion, anyway, but at the very least, I'd reboot the router.

Note that it's the weekend, the community moderators tend not to be here on the weekend. If you're interested in a quicker answer on your diagnostic, you should contact Sonos support on Twitter or Facebook.

Searches don't occur on your controller. They occur on your speaker.

Well that depends. Music Library searches occur on the speakers, but music service searches (and TuneIn) are done by those services in the cloud. In both cases the controller arranges the results to the user, merging them together in the mobile controllers (though not in the desktop, thank goodness).

If Browsing works on Spotify I cannot think of any reason why Search would not, as they are very similar APIs uding the same endpoints.

I did have one thought actually: what language/locale is your device/app set to? Some services do get confused when asked to search in certain "unusual" locales.