Hi Tess,

We appreciate your time for posting your concern here in the Microsoft Community.

Please follow the below steps to change the playback speed settings:

You can change the speed at which files play in the Player. For example, you can slow down the playback speed if you're taking notes while watching a training video, or you can speed up the slow sections of a presentation.

1. Play a file, and then switch to Now Playing mode.

If you’re in the Player Library, click the Switch to Now Playing button in the lower-right corner of the Player.

1. Right-click an open space in the Player (such as to the left of the Stop button) , point to Enhancements, and then click Play speed settings.
2. Move the Play Speed slider to the speed at which you want to play the file, or click the Slow, Normal, or Fast links.

To select speeds between the labeled play speeds, in the Play speed settings dialog box, clear the Snap slider to common speeds check box.

     3.  To hide the settings, click the Close button in the Play speed settings dialog box.

Hope it helps. Kindly update the status of the issue, we will be happy to help you.