Gran Turismo Sport had a small patch that was released, causing the servers to be down for two hours. That period is over at the time of writing and you should see a small update being downloaded on your PS4.
Developers Polyphony Digital stressed that the 1.07 update is not the content update scheduled for December, which will add another 12 cars as well as a proper single player campaign in the form of the GT League. The update is primarily to address an issue with the TCS driving aid- you would notice it’s easier to lose the backend of most cars when you throttle too early when exiting a turn. Full patch notes are available here.
Gran Turismo Sport’s biggest issue is its online-only requirement, which becomes a big problem if servers are going down so quickly. The game has so far has made its downtime more visible- a prompt appeared to warn of imminent server downtime that will not allow game saves.
Polyphony has also addressed this issue by allowing more modes to be available whilst not connected to the servers, but you are still not be able to save unless you go online again.