Depending on the display resolution and the scaling setting, the OK and Cancel buttons in the Player Configuration tool may have been pushed off the bottom of the display. Here are some things you can do, in Windows Settings, under System then Display:
- Change the display resolution to a setting taller than 720 pixels
- Reduce the scaling setting ("Change the size of text, apps, and other items") to 100%
You can always use the hotkeys (Alt+O for OK, Alt+C or ESC for Cancel) even if the buttons are not visible.