After the update which overhauls the UI of the game, the equip button of custom made skinpacks has dissapeared. this only happens with skinpacks imported using the skinpack addon system. storebought skinpacks work all fine. the enderman skinpack in the picture is a custom skinpack. as we can see here the button isn't there and therefore I can't equip the skin. as we can see in the second picture the storebought skinpack has a button as usual.