Julia, there's not a lot there to work with. For example is this your first time doing this or has something changed? What type of file you are trying to transfer. Etc.

I do not use Garmin but the usual problems stem from a 'break' between CT & Garmin. The general suggestion is to disconnect from Connect and reconnect through CT.

In any case this might help. Perhaps also a good idea to use the search box (top right of the screen) to find previous discussions. 

It is possible to bypass Garmin Direct and send routes directly to your unit as well. 

Thank you. I have done this some time ago but now it doesn’t work.

I used both the map and the journey routes, the taff trail showed up on the map but although it says yes it’s been sent to my garmin, nothing appears on it. I did try the search box but it didn’t help.

Sometimes Garmin sends back an unpredictable error, but I can’t see anything in this case.

Maybe worth making a tiny tweak to the route (just move a via point by a few metres!) then resaving with a new name, and sending it to Garmin after that. That will make it an all-new route and that might fix things.

I very occasionally have to use 'send to device' a route that's in the 'courses' folder on connect app, that route will then sync from the phone to my Garmin (Explore) the next time it connects, or I sync my phone if it is already connected.