Chiming in that this is affecting me too, along with a number of others over in this reddit thread.
Similar to others, the Shirt and Cape were correctly awarded while completing the activities, but not the Cap. All 5 activities show as completed in the event journal. Exiting and reloading the game client doesn't fix it. Logging out and relogging doesn't fix it. The Mojang Office cap does not show up under headware, nor does it show up under all appearances created by Minecraft. And I can't re-trigger the activities to try and re-earn the achievement.
enkinibiru
Chiming in that this is affecting me too, along with a number of others over in this reddit thread.
Similar to others, the Shirt and Cape were correctly awarded while completing the activities, but not the Cap. All 5 activities show as completed in the event journal. Exiting and reloading the game client doesn't fix it. Logging out and relogging doesn't fix it. The Mojang Office cap does not show up under headware, nor does it show up under all appearances created by Minecraft. And I can't re-trigger the activities to try and re-earn the achievement.