Capital Games just published the following on the EA SWGoH forums:

Hi Holotable Heroes,

We experienced some issues with the sign up period for the March 3rd Grand Arena overlapping with the Review period of the previous Grand Arena, detailed here. We will be rescheduling this event to start 3/5 and allow players the full time to join from 3/5/19 – 3/6/19 (Starting at 2:00pm Pacific/20:00 UTC).

Please note that the Grand Arena starting later today will be canceled with an update shortly and you do not need to set defenses.

So if you were stressing on which defenses to set for this latest Grand Arena event, no need to worry as you have some additional time now. Note that our Grand Arena guide here at Gaming-fans.com is getting a major facelift and new content is in the works, so be sure to keep checking back for more!