With the way Martinez sets up, I think it honestly could be Barkley where the problem lies.
Martinez in midfield plays 2 deep 1 forward. Barry does the job he's asked of him, drops deep to distribute and break up play, yes we all know he hasn't lived up to last seasons performances but that position isn't going to be the key in getting us going in my opinion.
Barkley on the other hand is the link between midfield and attack and let's be honest he's not very creative and he isn't going to get you 10 goals a season on a regular basis on recent performances although, I do believe he has the potential to, I just don't think he believe's it himself.
His link up play with Lukaku was lauded last season, this season they look like complete strangers.