Perhaps something is prohibiting the inspection agent from running? Does the app from the app store include the inspection agent like on the Windows install? Have you tried creating a custom package from the Connectivity profile under Access -> Connectivity / VPN -> Connectivity -> Profiles, highlight the profile, go to Customize Package -> Mac, Download and install? Is that a different application than what you're looking for and/or are trying to accomplish?
Typically in the past, when I've received errors indicating a session deletion due to inactivity (during the login process), it's because the inspection agent isn't relaying data to APM (usually because it fails to complete) - and hence fails the posture assessment. I run into this more so with Windows systems - but perhaps related.