Presumably the tasks you created on website are now listed under “Personal” in the tasks interface, so that should work.
Try on your phone clsoing the Tasks app then going to Settings > Apps & Notifications > Tasks > Storage & cache . Select “Clear storage”.
Open Tasks app again. Then force a sync like you did before in Settings > Accounts > etc You should get a new addition in the tasks app entitled “Personal”, with your e.email address included.