As many people already know, the latest Vanguard/Valorant patch f*cked up a lot of things, including that some users can't login to their PC anymore due to they keyboard/mouse aren't working after PC booted up.
This bug got reported a lot, as well as others and can be found:
(official Valoarant bug thread)
If you can't login to your PC anymore due to keyboard/mouse not responding,, there's a fix now:
1. Hard restart your PC by holding down the PC power button until it turns off
2. Start it again and see if your mouse/keyboard working now (Vanguard might fail to auto boot after that hard restart, which causes the mouse/keyboard to be working again)
3. If that didn't work for you, boot your PC in "safe mode". That's usually done by turning off your PC, turning it back on and pressing CTRL+F8 while it's booting up (you have to do that BEFORE your windows login screen pops up)
4. If you are in safe mode, you can turn off Vanguard in auto start (Task manager --> Autostart --> Deactivate Vanguard)
5. Once you managed to get back in to your PC again, you follow this fix in order to play Valorant again: (official reddit thread answer with fix)
Hope that helps a few