F5 Access for Mac OS client

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.