Solution
The error code 8150101A means that the command you sent to the Denso Robot is not possible while an Emergency-stop is ON.
You'll first have to check that :
1) The doors of the cage are closed
2) The emergency stop button on the cage is OFF
3) The emergency stop button on the mini pendant is OFF
Please also check that the MoveMode (M-Mod) option is set to X-Y on the mini pendant.
This error can also occur if the robot is outside its working area, or if the collision sensors are activated.
In order to put back the robot in the working area, you have to use the "override" option.
Please note that for this option, two operators are needed to unlock cautiously the robot.
Overriding of the test head emergency stop
On the head controller box, switch the button on "manual", then, depending of the head controller box you've got, turn the key switch or use a small pointy object in order to press the "Override" button.
By forcing the Override, you'll be able to move the robot from the mini-pendant.