the festival cape when in first person wont pop up on the elytra you are wearing

so i got the festival cape (pancake cape) and i wanted to see what it would look like on a elytra so i went on a test world to see but when i put the elytra on first person mode and looked at my character the elytra was invisible so i put the elytra off and put my self on third person mode and it wasnt invisible could you please fix this