Edit: everything is working well now. Enjoy your Disney+ stream time!
Although Disney+ has officially launched, good luck watching anything. It seems that Disney did not quite prepare for the influx of people that would be pounding their servers and things are off to a slow start. While you can sometimes view the main dashboard or add things to your watchlist, you might have to wait a few hours, or days, before everything starts running smoothly.
Check out more on the Disney+ clogged servers here: https://www.polygon.com/2019/11/12/20955914/disney-plus-down-slow-launch-day-the-mandalorian-error-76
Also, check out what is available day 1 on Disney+: https://www.polygon.com/2019/11/11/20956257/disney-plus-tv-shows-movies-full-list-star-wars-marvel-pixar-dcom
Image credit to Disney.