Use of Locus on a Samsung Galaxy Ultr (Gear OS) watch

I have recently started using Locus on my Samsung Android phone and my Samsung Galaxy Ultra watch. I quite like what I find but am puzzled as to why the start tracking button on the watch screen only functions if the app is open on the screen of the phone at the same time. If the app is not the current active live screen on the phone I get an error saying connection is lost and urging me to try again. If I do get it started there appears to be no problem in getting the watch app to stop recording the walk even though the phone screen is off.

I wonder if I might be using the wrong watch supporting locus app. When I set up the installation both the phone and watch apps came from Google Play. It appears that that watch app is intended for the Gear OS type watch. However I have trawled the Samsung store and failed to find anything related to Locus.

Is the problem starting recording from the watch a known issue? Do I need a specific Wear OS related app? If so, where can I find it?

Thanks for your time.

Mike O