The function of Steam Client is used to take screenshots.
Please confirm the following settings:
- If Steam Overlay while in-game is disabled, you are unable to take a screenshot.
In Steam Client > [Steam] > [Settings] > [In-Game], please check [Enable the Steam Overlay while in-game] to enable it.
- [Screenshot Shortcut Keys] is set as "F12" as default, but if you have changed it to any other key, please use that key to take screenshots.