We have received a number of reports that the Warfront can get into a state where it cannot be completed. It is being looked into, but I’m afraid we don’t have a workaround right now.
You can try leaving the Warfront and try again later, but the issue with those Warfronts is that the system will continue to back fill anyone looking to join the Warfront and keep that instance active. We’re looking into a means to address that, but one is not yet available. Sorry.
Edit: To clarify, as I don’t want someone to read into what I’ve said and use it to create their own narrative, I’ve edited the previous post.