There aren’t many options to be honest 
I’d recommend first debugging by clearing the entire Event Graph. Once that’s done, if the player character can indeed not move, move on by adding the IMC. If it still cannot move, add movement input on IA Move.
Perhaps we can gather some clues based on your observations.
However, you can have a quick fix by simply creating a new character, maybe along with a fresh player controller and an IMC. Or if you like you can as well create a new blank project, and migrate all of your assets to there if you’ve already made some advancements.
So, let us know how it goes 