Garmin informed some people (not me, I had to waste 3 hrs) that due to some infrastructure change, pc/mac sync may fail with one of several server errors. Here is the fix. Would be nice if Garmin had some way to communicate breaking changes to their customers. Even a sticky post is better than nothing.
https://support-inreach.roadpost.ca/kb/articles/unable-to-sync-reinstalling-the-inreach-sync-app