Since the release of macOS High Sierra, some extensions must be approved for the corresponding applications to work as expected. This includes your Intego software as described in the article Allowing Intego Extensions in macOS.
There is a known issue in macOS which may cause this process not to work as expected in some cases. You can read more about it in this Apple discussion thread.
To resolve the issue, a user must either temporarily disable SIP and then re-enable it after installing the software or; perform a clean reinstall of macOS. If you choose to temporarily disable SIP, it is important that you uninstall the software, disable SIP, then reinstall the software again.
How To Disable SIP:
Boot macOS into Recovery Mode. To do this, restart your computer and hold down the Command+R (⌘+R) keys simultaneously when you hear the boot chime.
Once in Recovery mode, open a Terminal window from the Utilities drop-down menu at the top of the screen.
Type the following into the Terminal window: csrutil disable
Press the Enter/Return key, and you’ll see a message stating that System Integrity Protection has been disabled and that the machine needs to restart for changes to take effect.
Now, restart your Mac and SIP should be disabled. You can now install your software without any conflict from this service.
How To Re-enable SIP:
Once you have installed the software, restart in macOS Recovery mode again with the Command+R (⌘+R) keys, then open a Terminal window and type: csrutil enable
Press the Enter/Return key, and you’ll see a message stating that System Integrity Protection has been enabled and that the machine needs to restart for changes to take effect.
Restart your Mac and SIP should now be working again as expected.