Are you connecting the output from the X8R to the Pixhawk RC input port as shown below?
You can also read some more info on this as someone else has a similar issue on connecting X8R to Pixhawk
Hope that helps 
Are you connecting the output from the X8R to the Pixhawk RC input port as shown below?
You can also read some more info on this as someone else has a similar issue on connecting X8R to Pixhawk
Hope that helps