SAG-AFTRA said it celebrated the rights of artists - such as James Earl Jones’ estate - to use digital replicas, but said Epic Games did so “without providing any notice of their intent to do this and without bargaining with us over appropriate terms.”

I had chosen that source just for the best headline for the meme, but turns out it also had a succinct answer to your question. Jones’ estate consented but SAG claims the way Epic went about implementing it violates contracts between Epic and SAG.