Command was denied by ardupilot

I’m trying to test my motors using ardupilot 2.8
when I use the “TEST MOTORS” command, the mission planner show the following notification:
“command was denied by ardupilot”
Can anyone help me?

Hello, did you find a solution to this problem? I have the same trouble getting to test the motors. Thanks

Hi , have you armed?

Hello, no I don’t think I have. How can I do that?

Yes, it worked now! I had to arm it of course. Thanks a lot