After moving my unreal engine from 5.1 to 5.6 my character is broken.

Hello, I recently moved my unreal engine project from 5.1 to 5.6 and for some reason my character is broken now. It is saying that I have bones missing. I had built IKRetargeter from 5.1 and now none of my animations work correctly any more. I am using synty character. Thank you for responding.