Now this is just MY problem. YMMV.
My problem was I simply couldn’t see how to upload new activities. With the old site layout there was an upload button up the top. Click it, upload, job done, view activities and so on. The new layout doesn’t have the button, it wasn’t in any menu, Sync asked me to install Garmin Express, the Help didn’t help as it referred back to the old layout. Hence this mornings question.
I had installed Garmin Express a few months ago to see what else that could do. I only have a basic Forerunner watch so all it seemed to be for me was just another lengthy step to uploading. (I accept that Garmin Express and the new site are probably much more useful for those with fancier Garmin gadgets than I have, downloading routes and maps, etc.) So deleted it and stuck with uploading through the site. Having installed it again I have been reminded how unhelpful it is to me.
Now the new site interface looks very pretty and all, just need to see if the shiny new bells and whistles are worth the more annoying method to get anything on it or if other sites do the same without the hurdle. I can obviously upload and view stuff on the Strava website with just a couple of clicks without needing a separate bit of software for the first step.