I had an issue today when I went out to pick up some lunch. Couldn't connect to Spitfire over the cellular network when I was in store.
I am able to connect to my vehicle when my phone is connected to Wi-Fi (even though the car isn't). For that matter, I can't connect to anything over the cellular network leading me to believe that the issue is with Rogers' service as opposed to a problem with Tesla's service specifically.
EDIT: I've now also verified that I can remotely connect to my home PC systems so there's no issue with Rogers' Internet service. It would appear to strictly be a cellular issue.
EDIT2: Rebooting my phone seems to have fully cleared up my connection issues completely.