1.13.0 Has been rushed, unfortunately. There seem to be more glitches then features!
One of these glitches is invisible custom skins. It is effecting Minecraft, Lifeboat, Hive, Mineplex, CubeCraft, InPVP. The character's custom skin appears to be broken and simply is invisible.
Thank you for your report!
We're tracking this issue under MCPE-50094 so I've requested this report be resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
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