I had the exact same issue when creating a MainMenu Level so that my game would not launch without pressing Play. I searched here and everywhere else My inputs were correct and nothing worked…
THIS WORKED… I went into the character BP, I opened “Class Settings” and changed the parent to an Actor, and then back to a Character Class. The issue with movement is a bug within your character BP where it is no longer registering it as a Character even though it claims to be one. So it appears that everything is fine when in reality to your project there is no existing character.