So sick of this. Search still doesn't show results from shared notebooks. It used to work a long time ago, but doesn't anymore. This issue is the main reason I'm migrating my family off Evernote as soon as I can find the time. Affects me on old web client, new web client, and Android app.
Experiencing same problem. Android 6.0. I am able to search only my own notebooks, not shared notebooks. I get zero results when I attempt to search while looking at a shared notebook. I do not have this issue when using the Web client.