I’m still on 5.15 but got a software update notification almost two weeks ago and the software update I received will not upload. Called Tesla’s helpline and told me to try again over the next week and if I don’t get a new update to contact them again. I emailed them and haven’t heard back yet...I’ll probably swing by the Service center to see if they can upload software for me there.
If your update notification was for 2019.8.3 and you were later not able to update, it was likely because Tesla pulled the release. I have heard of this happening to some people on the forums, and while I was on a call yesterday with Tesla Support, they had mentioned that 8.3 was pulled. If you have time to kill, you can always walk into the service center, but with the frequency of updates recently, you may want to wait it out.