Subject: Error 4412: Notes Error - Specified command is not available from the workspace.
Subject: explanation
The error means what it says. You are trying to do something (run an agent or a smarticon/toolbar item, or something) that cannot be run against the workspace. It probably needs you to be open to, and clicked into, a view, or select a document, or something.
It would help if you had posted some description and/or a code sample.
Subject: This might answer your question