"Dynamic Link Media Server failed to launch / Slideshow playback is not possible due to an error.

Hi there,

We're sorry about the trouble with Lightroom Classic. Would you mind sharing the version of Lightroom Classic you're using? Which file format are you working on? Is it possible if you can share the screenshot of the issue?

Try to run Lightroom Classic as an administrator, do the following: 
1. On the Start menu, locate the program that you want to always run as an administrator.
2. Right-click the application’s shortcut, and then click Properties.
3. In the Properties dialog box, click the Compatibility tab.
4. Do one of the following:

• To apply the setting to the currently logged-on user, select the Run This Program As An Administrator check box, and then click OK.
• To apply the setting to all users on the computer and regardless of which shortcut is used to start the application, click Change Setting For All Users to display the Properties dialog box for the application’s .exe file, select the Run This Program As An Administrator check box, and then click OK twice.

Note: Make sure you've closed Lightroom Classic from the Task Manager.

Let us know if that helps.

Regards,

Tarun