As a very active, heavily invested Guild Leader with a busy life away from the game, I've now missed joining TW twice in past 2 months, after never missing any previous to that.
Several other members have also missed joining because the automated reminder passes quickly in the chat window at times and thus, easy to miss. I don't always have time to track everyone down who havn't joined.
At a minimum there should be a red dot alert on Guild Events drawing attention to the Join being active.
Perhaps an automated email announcing Territory War Join period has been launched.
Or one of those nice event buttons on right side of main Cantina screen with "JOIN" in it.
We're incredibly frustrated with this change you made in the launch of TW.