Robotic arm position error with moveit

Hi everyone, I'm trying to apply what I'm learning about robot manipulation to a real robotic arm like this one: https://www.thingiverse.com/thing:2433 I've created a first xacro file that should rappresent the robot. Now the main problem is that when I try to execute the motion script giving for example the following pose (that is something that the robot should be able to reach because is tall almost 40cm):

orientation = tf.transformations.quaternion_from_euler(0,-1,1)
pose_target.orientation.x = orientation[0]
pose_target.orientation.y = orientation[1]
pose_target.orientation.z = orientation[2]
pose_target.orientation.w = orientation[3]
pose_target.position.x = 0.11
pose_target.position.y = 0.1
pose_target.position.z = 0.122

I get the following error:

Error:   RRTConnect: Unable to sample any valid states for goal tree
         at line 215 in /tmp/binarydeb/ros-kinetic-ompl-1.2.1/src/ompl/geometric/planners/rrt/src/RRTConnect.cpp
Info:    RRTConnect: Created 1 states (1 start + 0 goal)
Info:    No solution found after 5.005102 seconds
Debug:   Attempting to stop goal sampling thread...
Debug:   Stopped goal sampling thread after 0 sampling attempts
[ INFO] [1536085998.374417705]: Unable to solve the planning problem

I thought that the problem was the fact that the solver that moveit uses is for robots with 6/7 dof so I've added another dummy link to the robot. Also when I launch the demo.launch file that is created by moveit I've noticed a problem, for example in this position

I'm not able to turn the wrist so that the finger can point to the ground, maybe this is the reason that make the solver fail. However if for example I press a "random valid" position in RVIZ the wrist assume a position like this

that I'm not able to do moving the marker manually, and also starting from this position I can't move the robot in any direction. Do you have any suggestion? At the moment would be nice just put the gripper in a givent point in the 3d space without concerning about the particular orientation. Thanks for your time