This is a problem that has existed for years and the proposed solution given in this support community does not work!

In my case it's 5 Amazon Echos configured in multiple multiroom setups. These work eg via Amazon Music without any problems. They show up and can be activated individually.

However, via Spotify Connect only 2 of these Multiroom groups are displayed (no matter if Android App, Windows App, ...). Deleting / adding / renaming of the not shown groups doesn't have any effect. There are simply never more than two groups visible in Spotify.

All Echos are on the same network and all groups work without problems in other music services. So I cannot believe that the problem lies within Amazon.

Spotify, finally get this fixed!