Interesting. Have you submitted a system diagnostic within 10 minutes of experiencing this problem, and called Sonos Support to discuss it? It sounds like either Sonos isn’t sending the request for information (less likely, since all the other streamers seem to work) or the Bandcamp servers are not responding with your data for Sonos to show. 

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

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Given that other streamers seem to be working, I’d be tempted to ping Bandcamp’s CS as well, in case the issue is on their side. 

I was working with a support engineer for about 30 min, and it turns out this is a known issue. They aren’t publishing anywhere the status of this, so the recommendation was to try again periodically and see if it works. Really want to be a fan again but man...

Glad to hear they’re aware of the issue, and working on it. Thanks for your time in working with someone!

Try the Desktop app - Search went through some shenanigans on the mobile app, going through the cloud, which isn’t compatible with every service. Desktop app still does “old-school” search,

It’s never worked for me, I’ve done the same as JaimecafeR.