From the stories it sounds more like the agent wants a massive pay day and we're not exactly renowned for facilitating that sort of thing - maybe if Don Raul was still around. It would be an easy sell for Vlahovic too, yeah Arsenal are great, but imagine playing for x, y or z.
From Vlahovic's point of view, as exciting as our young squad is to us, it's probably not created enough hype just yet to sell it as an exciting project for another young player in the absence of CL or European football. So if the agent isn't really selling it to him or pushing for it to happen, then it wont.