David Ogilvy once said that, in the end, making an ad comes down to one person shutting the door and just putting it down on paper. Okay, so there are no more offices. Or doors. Or paper. Or David Ogilvy. You get the point. Sometimes you gotta go DIY.
Cease with all the co-creating, hot-housing, workshopping, brainstorming and other effete delaying tactics. Go find a quiet place and find an idea.
Once you have it, go back into that room and see if you can sell it in. And remind yourself to never, ever walk into a groupthink without a couple of ideas in your pocket.