If you are using the new flower Cape, and are wearing it with the elytra, you will not see the Cape or the elytra on the back of the players skin.
Comments 2
Cleaning up old tickets: This ticket had been set to 'Awaiting Response', but has not received a response from the reporter (~3 months+) so is being closed as Incomplete. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines which includes steps to reproduce the problem.
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Does MCPE-63117 describe your issue?