spanning with mini mac and two monitors

[nomadicslowaction]

HI, I am having trouble entering the spanning mode on arraysync and urgently need help as this is for an exhibition opening tomorrow. I am using to stacked flat screen monitors and have created a video file at 3840 x 1080 to be able to span across both monitors. I have used arraysync in the past for the same piece and it worked smoothly. So what happens is that it shows either the full video on both screen simultaneously or if I use the offset function it just shows one part (albeit correctly) but not the other. any advice help would be greatly appreciated

[Turboladdade]

Have you checked that you disabled spaces? Have you verified that your screens are arranged properly (one on top of the other) in System Preferences?