Short version: On Events tab, the "New" button is grayed out, and when you mouseover it says you can't have more than 16 events. However, no events are listed or upcoming, so the system must be counting ended, cancelled, and/or deleted events against that total of 16.
I've made multiple bug reports on this issue (2 in-game, 1 through website) over the past 2-1/2 weeks or so, and I have yet to hear any response at all.
Can you have someone look into this please?
For whatever reason there is a missing patch note, but that bug is fixed in this build.