Guild Wars 2

Our guild [WHB] just completed this Guild Challenge mission: Scratch Sentry Defense and did not receive guild merits for doing so. Everyone involved received their personal reward chest for participation in the event.
However, the guild has no merits to show for it, and the challenge remains active in the guild missions log as if we never activated it(Picture 1).
In Picture 2, you can see we are nearly finish the mission.
And in Picture 3, you can see we have already finish the guild challenge mission and everyone received the chest.
I also still have the option to activate the guild mission at the site of the challenge.

Picture 1: http://holland.pk/uptow/i3/57bd7b997be45e2658ae90b2c139e083.jpg
Picture 2: http://holland.pk/uptow/i3/96613c60168e5762d0e9042cc4dc2d9c.jpg
Picture 3: http://holland.pk/uptow/i3/1bf4836c457156d8bed8b2fbb68c7071.jpg

Same thing happened to our guild, but, with some quick thinking from our guild leader, we figured it out.

If you have more than 220 merits, then you will not receive the reward because the merits cap at 250.

So what you have to do is queue something so that you have room for more merits. We got the guild reward after completing the guild challenge again.