I never got the option to join Grand Arena.
There was not a tile on the front screen, and when I went into the grand arena tile I got the message "No Grand Arena events are active at this time."
Please note that this was yesterday (21/12/2018-22/12/2018)
I am active and was on multiple times during the day so you should be able to see any logs if they exist to support this.
Ally Code is 686-827-438