@Bill-Stephens I have found that MyDrive syncing can behave unpredictably at times. What helps me in that situation is to disable and subsequently re-enable the synchronisation toggle in MyDrive (don't know if the MyDrive app on the phone has it, but the website certainly does) or even just changing the name/description of the route.
But this has only occurred for me in the TomTom Go app on my phone (routes not syncing even though the sync toggle shows as enabled in MyDrive). On my actual TomTom device, the only way routes were not syncing, was due to me not having the sync toggle enabled in MyDrive.