I have a garmin coach plan which is not syncing with my watch. When I look into "Training Calendar" shows "Download your training from Garmin Connect".
I've already synced many times through app and nothing is appearing.
I had a half marathon training plan in my Training Plans area of connect.garmin.com, and it was showing in my calendar in the web and on the iOS app. I would try to sync with Garmin Express from my Mac etc., it would look like it was syncing, but as you found, when I went to my FR620 I only saw "download your training calendar...". iOS syncing has always been hit and miss for me, so that didn't work either.
To effectively force the training plan to sync, I had to create dummy workouts and events and add them to the calendar on the web. Then sync.
I had my FR620 connected to my Mac. On the web app, I created a couple of workout runs manually around the current date (where I had some Training Plan workouts in the calendar). When you create the work out (warmup/run/cool down) then click Save, you should see an option to 'Send to Device' on the right side. Then it opens Garmin Express, and should sync. As an extra step (though I don't know if it was necessary) I would additionally drag the workouts onto the calendar. Then you get a notification at the bottom of the screen saying something like 'this will appear in your calendar the next time you sync'.
I had Garmin Express open, so click the sync button a couple of times. Then when I ejected my FR620 from my Mac, the watch screen says "Updating".
FINALLY. My training plan runs are showing up on my watch. I guess you could delete the dummy events/workouts again, but the whole sync is so fragile I've just left them on my calendar.