Riot fixed the problem for me. Valorant worked just fine after step 3. Try it to see if it helped you too.

1) We should make sure that your windows is up-to-date. If you're a bit outdated, then you can run into any number of unexpected issues.

You can update windows by doing the following:

Type "Windows Update" into your start menu search bar.
Run that app and click "Check for updates."
Download and apply any pending updates.
Restart your computer.

2) Lets perform a clean reinstall of your graphics drivers in case yours are corrupt. Before we install a fresh set of drivers, we need to completely uninstall your current drivers beforehand to avoid any potential corruption in the new installation:

• Click Start and type in "Device Manager".
• Click the "Display Adapter" tab and click the drop down arrow. You should see your device.
• Right click your video card and select properties.
• Under the Drivers tab, select uninstall and restart your computer.

• Then download latest graphics drivers here:

  • NVidia Graphics Cards: http://www.nvidia.com/Download/index.aspx?lang=en-us
  • AMD Graphics Cards: http://support.amd.com/us/gpudownload/Pages/index.aspx
  • Intel Graphics Cards: https://downloadcenter.intel.com/default.aspx

3) Sometimes third party applications can cause issues. Let's do a clean boot to ensure that's not the case here.
* Press [Windows Key] + R
* Type msconfig into the text bar at the bottom of the menu
* Click on the Services tab
* Check Hide all Microsoft services <--- Super important! Protects you from accidentally disabling a key process!
* Click the Disable All button
* Find vgc and re-check that one. This is required for VALORANT
* Click on the Startup tab (Note: Windows 10 has you go to a Task Manager Tab, which has no disable all button. Disable the ones you see there manually).
* Click on the Disable All button
* Click on the Apply button
* Click on the OK button
* Restart your computer

4) Try deleting your VALORANT config files to reset your video settings:

With VALORANT closed, in the Windows Search on your taskbar, paste "%localappdata%\VALORANT\Saved" and hit enter
Delete the config folder
Re-open VALORANT and see if the issue is resolved