Nothing happens when I click star to export my tracks to GPX as I have always done
My guess is that it is something that is blocking the downloads. The web browser or an extension.
Do you get the same behaviour in other sites like for example Strava?
Running in incognito mode with no extensions activated should give the answer if it is an extension causing it.
You can check the direct link (add ID):
connect.garmin.com/modern/proxy/download-service/export/gpx/activity/***ID***
Or load the page → open DevTools (F12) → switch to the Network tab → try to export using the button, and it will show a status (green or some error) or nothing if there is a problem with clicking itself.