Last time I checked, Native Access 2.6.2 was not able to install a library to location on external drive on macOS. I read somewhere that NA should be granted full access to disk. Yes tried that too, and now I have tried to install the same 45GB library three times (and every time it wants to start downloading it again..) - so I'm asking would it be possible to just do a simple check in the NA software whether it is able to install anything to the selected location before proceeding.
The nicest thing would be to actually fix the issue.