Newbie Can't get APM Copter 2.8 to "arm"

Hi, everyone new to UAV, have a S500 Frame & Futaba T7C in aero mode. I have a good 3D gps lock. in the esq cal all motors run fine but the motor test is dead. Any or all help very appreciated. Thanks Dave
PS: all is working fine now.

PS :I redid the motor test and I upped it to 9% and all ran fine.