After a lot of searching, I've discovered the root of the issue with why players are unable to get Riot Vanguard to work as of the past 24 hours.
A patch was pushed that updates the kernal-level driver for Vanguard (vgk) from 0.3.0.9 to 0.3.2.2. After the patch, the system level service for Vanguard (vgc) no longer starts, whether manually or by Valorant during boot up. Regardless of how many times you attempt to re-install it, if will always install the new 0.3.2.2 version and will remain broken.
It's worth noting the symptoms are identical to previous issues with Vanguard, which is misleading for many people as solutions have been posted in the past and they will no longer work. The service is installed, but it cannot be started.
This is not an issue with your machine or installation, likely a bug with the new version.
I'm going to send an email to Riot support with any information needed, whether it's system logs, dxdiag dumps, or anything else of relevance, but I was able to reproduce it on multiple machines. For now if this is an issue you're having, sit tight and don't pull your hair out because other solutions aren't working.
You can use a program called DriverView to check the version of vgk that you have, but I believe the patch is being pushed to everyone and there's not much you can do to stop it, so we may just have to wait.
EDIT: Learned that this is not actually happening to everyone. In fact, only a minority, but still enough to be considered widespread. I've done thorough testing on every variable I can think of to no avail. Thank you for all of your data and input though, every little bit helps even if it's just "works for me" that's still data. I have tried all of the solutions mentioned in these comments, and the comments of every thread I've found on this subreddit, and I've dug through a baker's dozen. I'll update this with any more information, but I've given up. Beyond re-installing Windows or waiting, there is no solution in sight.
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