To restore Rocket League to the default video settings:
- Click on the yellow folder icon in the bottom left corner of the screen
This will open File Explorer - Click on Documents in the left-hand column
- Click on My Games
- Click on Rocket League
- Click on TAGame
- Click on Config
- Right-click on TASystemSettings
- Select Delete
This will delete any custom settings. You should now be able to launch Rocket League with default settings.