Can you change your GameUserSettings file in a couple of places for me? There are two to check: C:\Users\%USERNAME%\AppData\Local\VALORANT\Saved\Config\WindowsClient - GameUserSettings and C:\Users\%USERNAME%\AppData\Local\VALORANT\Saved\Config(some long string of letters and numbers)
With the game closed, go to both of those files, and change these two lines:
ResolutionSizeX=1920
ResolutionSizeY=1080
LastUserConfirmedResolutionSizeX=1920
LastUserConfirmedResolutionSizeY=1080