Many of us experienced this as well, myself included. The way I understand it is that Tesla gives you temporary access when you take delivery to connect your phone to show you how phone as key works and to make sure it works in the first place. At that point you are still not considered the owner of the car in Tesla’s system. If you are designated the owner in Tesla’s system fairly quickly then you may not notice any temporary hiccup in access from the phone. But if whatever they need to do on their end takes a little while then you will have a period of time where you don’t have access from your phone. When this happened to me I first noticed it a few hours after I took delivery but my access was restored just a few hours later.
Tesla really needs to do a better job of warning people about this during delivery or better yet figure out how to change their backend processes so that it doesn’t happen in the first place.