We had installed the ULM Update in KB 235538, but were still having issues with the SEP for MacOS import.
This error is seen in the SMP Logs:
Error while parsing .pkg: Failed to load 7z.dll, file is missing in local directory or in 'C:\Program Files\Common Files\Altiris\7z.dll' dir.
We added NTFS permissions for Everyone to C:\Program Files\Common Files\Altiris, and that allowed the Import to complete successfully. The App ID did have Full Control of this folder previously, so were not sure why this worked.