Is there any other difference than name of the activity in the Garmin Connect? E.g. frequency of the GPS reading, points tracking or... or maybe the most important, distance measured in 3D (not just the vertical projection)?
Formerly I had Amazfit Pace and as every Amazfit sportswatch it has the ability to switch on the 3D measuring of the activity distance. If you hike over mountains with a lot of elevation the distance is significantly higher then.
This is what I meant:
support.garmin.com/.../
Of note: you can copy a sporting type file from one Garmin to another, but there's no guarantee it'll work.
Example: WalkingWalk_Indoor.fit is the "Walk Indoor" activity found on the Forerunner 245. Copying that file to a 945 adds it to the 945.
You could try doing same with the Hike.fit file from a 945...but there may be compatibility issues going from a Forerunner (5-button non-touchscreen) to your Vivoactive. (.fit files from my friend's VA3 were unstable on my 945)
Regardless: I've attached "Hike.fit" from my 945 inside a ZIP file. Unzip it, give it a shot and let us know how it works. It goes in the "Sports" folder if you're browsing your device from a desktop computer.
I have copied it to Sports directory, restarted the watch, but I don't see the activity on the list - neither on the watch or Garmin Connect.
You have to go into settings and add it.