Windows 10 won't update past 10586.545

The irony. People whine 'cause Windows 10 won't let them disable automatic updates, and I can't get them to work on my PC. Hah.

Anyway, so the story goes I decided to look up Forza Horizon 3 on the Microsoft Store to see if the demo was out. And while it shows up in the search list, when I try to bring up the page it says "The thing you're looking for isn't here". I did some digging and it turns out I need the Anniversary Update for it to work, whatever that is.

After consulting a friend who has the4393.105 version of Windows 10 (latest one, according to him) I realized that I'm several updates behind, as my OS is version 10586.545, which doesn't even include the necessary Anniversary Update.

I didn't do anything to disable the updates, nothing that I know of. I disabled Windows Defender, but that was right after upgrading from 8.1 back in March and I did receive updates afterwards up until the beginning of August. Also "Check for updates" says I have the latest version.

The Anniversary Update was released to market on the 2nd August. It is being rolled out in phases through windows update. Your updates aren't disable, it's just that it's not your turn yet. More on the phased rollout here:
How long do I have to wait for AU to be seen by windows update

You are running Windows 10 Version 1511 (OS Build 10586.545). This is the Fall Update release last November with its latest Cumulative Update from 2nd August 2016. Yes, you are completely up to date. You will in due course be offered the Anniversary Update (version 1611) through windows update, but if you can't wait you can start the upgrade yourself. To find out how, see...
How to get the Windows 10 Anniversary Update