Paul started filming his lastest SGA episode 'Identity' this week, including working all day on friday (22rd Aug) and would need to be in the studio Monday morning. He has never missed a show before, and would never miss a show for any other reasons. In May in fact, he finshed shooting friday afternoon, got on a plane right from the studio and flew in, coming straight to the event in Milton Keynes directly from the airport.
Both he and Showmasters worked really hard to make it work, unfortunately they just couldn't make the schedule fit and filming commitments come first. Paul's already said he's open to come back in December if fans want to see him and he's available.