Hi,
What you have encountered is an over zealous “Gatekeeper” that is inbuilt to the Mac OS.
Read this, which will save me having to type out the same old thing one more time.
https://support.apple.com/en-us/HT202491
Oh, yeah, what “crusininon2” states above is technically correct - with the latest update you should not need the Line 6 updater. Although, when you do the latest update (v2.92) using the HX Edit install routine, you will probably find that it is actually running on top of the Line 6 Updater app. If you have any grief trying to update through HX Edit, simply fire up the Updater and do it through that app. In fact to avoid any issues with the Line 6 servers, download the latest software to your drive and do a local install. During the update do not allow your computer to go to sleep, in fact do not have anything else open or running on your Mac.
Hope this helps/makes sense.