barry - I have two TomToms and I can sent a route to both from my laptop. The TomTom is logged into my account; when I bring up MYdrive on my laptop it asks me to login. Once logged in the laptop can see all the saved things on my TomTom (favourite places, routes etc) and they are displayed on the map. I ask it to plot a route, modify it if required and then hit the "Send Destination/Send Stops" button. I get a message in the top RH corner of the map "Syncing Successful".
Next time I go out to the car the TomTom comes to life and, after a short time, I get a message "New destination received" and it plots a route. You have to have your TomTom logged in to your account and then log Mydrive in but it works every time for me. Because I have two TomToms the destination is sent to both.