The simple sprint code that the Instructor showed is not multiplayer friendly. It will have your character moving at different speeds client and server side, so you will have desync issues.
This is what I did. May not be perfect, but it seems to work for me.
Edit: I forgot to mention that the Walk_Server and Sprint_Server nodes are “custom events” and their properties need to be set to “Executes On Server.” You can see all of that from the screenshot if you already know what it is, but I’m sure some people in this course won’t know that.