No Grand Arena - No notification - failed to join

In general, these types of issues are really hard to evaluate after the fact. There have been similar issues with Territory Wars and people joining (or not joining). ☹️

The best advice I can give you right now - when an active GA join period is open, if it's not visible to you (either on the right-hand side of your screen or in the GA table icon), that 24 hour period is the time you need to come here and post for help. QA Support might be able to check your account at that time and see if there's a problem.

After the GA matchmaking has happened, there's no way to insert you into the round.

I strongly recommend everyone's guild discuss it and call it out when the round starts. I'm a guild leader, and I always update the guild banner in game to let my guild know it's active and that they should sign up. My guildmates playing and getting rewards just makes my guild stronger, so I want them all to do it.