Are you on regular or user&device mode?
Idea 1: lack of permissions in /etc/asterisk/manager.conf
Idea 2: you are in user and device mode with a broken userdevice.agi (as it comes stock in freepbx), you can somewhat overcome this by setting the originatechannel to Local/xxx@from-internal in all extensions in the fop2 buttons page.
Best regards,
