When you start the game and try to start a world it will say skin is not multiplayer friendly and you must change it . after you change it even though this skin used to work before 1.12.0 it will no longer allow people to join your world and never lets them get through the locating server phase. I have only witnessed this bug after the 1.12.0 phase and its no longer allowing multiplayer.
Linked issues
Comments 4
Thank you for your report!
We're actually already tracking this issue at MCPE-48494, so we will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Which skin are you using?