Interesting! So you are getting data back from the /v1/instrumentation/content/visits endpoint, and you just cannot find that content_guid in the responses?
If people have viewed the application, it definitely should have data there! Are you a publisher / collaborator on the content, or an admin? If you are not a collaborator, then you will not have access to see the data about the application unless you are an admin.
Related, have you seen this report? It could show some patterns to follow for retrieving data.
The former doesn't yet support that I'm still reasoning through what that would look like (filter methods, API specific helpers, etc.).
The latter does, though! The arguments to get_usage_static() should get you started. The time formatting may be a bit rough - there are definitely some rough edges Please feel free to file issues!