Source flip book for sprite component will not change

I have followed this tutorial (Paper 2D #5 - Top Down Character Full Process - Unreal Engine 4 - YouTube ) almost exactly step by step, simply using a different map, and different sprites to make a different set of character flip books, but when I get to 15:35, where he chooses his source flip book in the viewport of NewCharacter, I select the flip book I’d like as my “idle” and nothing happens. The drop down menu closes, but the source flip book still says none, the save button also changes to compile as if something’s changed even though nothing has. I don’t know what to do. Please help, thank you.

I had no problem downloading the book