What I expected to happen was...:
When in the Realm menus I attempted to change the difficulty from Normal to Peaceful.
What actually happened was...:
It never changed and stayed on normal, despite me even reuploading my world on peaceful.
Comments 2
You need to be the owner of the realm and then go through the realm settings, not the online menu. What difficulty the world was on before it was uploaded is irrelevant. See MC-191068.
Do the tips in MC-191068 help?