Your NS was communicating with agents via HTTP and you have reconfigured the communication method to use HTTPS. The IIS was configured to require SSL and the codebases were changed to publish HTTPS. However even after running the NS.Refresh Packages and the NS.Update Distribution Point the ULM agent is failing to install reporting the following the error :
Checking Client connectivity and free space - Failed
In status report > [View log]
INFO: SHA 256 Integrity check succeeded.
INFO: Getting Package : http://<<NS FQDN>>/Altiris/NS/NSCap/Bin/Unix/Agent/Mac/x86/package-manifest.xml into temp dir /opt/altiris/notification/nsagent/.tmp_inst
INFO: Failed getting package, Msg: HTTP server returned an error