I went to open my Glory keys and was greeted with this message…
Clicking okay and reloading the Chests tab fixed it. I didn’t lose my keys, I just figured it should be noted as I couldn’t find any similar posts.
You most likely accessed the chest menu as chests changed over (to put the other mythics back into the chests).
Ah! Alright. That makes sense since it was around 7:00 UTC. Thanks.