A SEP 12.1 RU5 install package for Macintosh has been imported into an older verion of the SEPM. Exporting the RU5 package from the SEPM and attempting to use it to install SEP on a Macintosh results in "Install Failed" error message.
Install Failed: Symantec Endpoint Protection Installer has been modified
Installation has failed because we cannot find the necessary installation files that are required to install Symantec Endpoint Protection for Mac
This behavior in the older SEPM is by design.
The SEP 12.1 RU5 Macintosh installation files come now with the "Additional Resources" folder separate from the installer app.
But in older versions of SEP for Macintosh the "Additional Resources" folder is incorporated inside the installer app. When an RU5 Macintosh SEP client is exported from an older SEPM, the SEPM exports it in the older format. The installer for the exported RU5 package fails because it is looking for the separate resources folder, outside of the app.
The exported RU5 package may be fixed in the following manner: Unzip the exported RU5 package on a Macintosh. Right-click the "Symantec Endpoint Protection Installer" and choose "Show Package Contents". Go to Contents and move "Additional Resources" folder out of the app so it is in same directory with the Installer. Then the installer will run without error.