MoveIt /compute_ik gives no solution (error -31)

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I'm trying to the joint values for a robot arm given a specific target pose of an object. The code is below in FlexBe state format and gives Error code NO_IK_SOLUTION=-31. The full print of the result can be seen in the end. Hope you can help me :)

class MoveItIKState(EventState):
'''
Computes the joint configuration needed to grasp the part given its pose.

-- move_group       string[]        Name of group to be moved
-- offset           float           z-offset above the object
-- end_effector     string          end-effector link

># pose             PoseStamped Pose of the part to pick
#> joint_values     float[]     Joint values for grasping
#> joint_names      string[]    Names of the joints

<= continue                 If a grasp configuration has been computed for the pose
<= failed               otherwise.
'''

def __init__(self, move_group, offset, end_effector):
    super(MoveItIKState, self).__init__(outcomes = ['continue', 'failed'], input_keys = ['pose'], output_keys = ['joint_values','joint_names'])
    self._move_group = move_group
    self._offset = offset
    self._end_effector = end_effector
    self._service_available = False
    self._service_name = '/compute_ik'

    self._tf_buffer = tf2_ros.Buffer(rospy.Duration(10.0)) # Buffer length
    self._tf_listener = tf2_ros.TransformListener(self._tf_buffer)

    try:
        rospy.wait_for_service('/compute_ik', timeout=5.0)
        self._compute_ik_service = ProxyServiceCaller({self._service_name: GetPositionIK})
        self._service_available = True
    except rospy.ServiceException as exception:
        Logger.logerr("Service call failed: {}".format(exception))
        return 'failed'

def execute(self, userdata):
    if self._service_available == False:
        Logger.logerr("Service is not available, state failed...")
        return 'failed'

    print(self._service_result)



def on_enter(self, userdata):

    try:
        self._target_pose = self._tf_buffer.transform(userdata.pose, "world")
        self._target_pose.pose.position.z += self._offset
    except Exception as exception:
        Logger.logerr("Could not transform to world pose! " % exception)
        return 'failed'

    self._service_request = GetPositionIKRequest()
    self._service_request.ik_request.group_name = self._move_group
    self._service_request.ik_request.robot_state.joint_state = rospy.wait_for_message('/joint_states', sensor_msgs.msg.JointState)
    self._service_request.ik_request.ik_link_name = self._end_effector
    self._service_request.ik_request.pose_stamped = self._target_pose
    self._service_request.ik_request.avoid_collisions = True

    try:
        self._service_result = self._compute_ik_service.call(self._service_name, self._service_request)

    except Exception as exception:
        rospy.logwarn("ERROR 1")
        Logger.logerr("Could not call IK: " + str(exception))
        return 'failed'

Output of self._service_result:

solution: 
  joint_state: 
    header: 
      seq: 0
      stamp: 
        secs: 0
        nsecs:         0
      frame_id: ''
    name: []
    position: []
    velocity: []
    effort: []
  multi_dof_joint_state: 
    header: 
      seq: 0
      stamp: 
        secs: 0
        nsecs:         0
      frame_id: ''
    joint_names: []
    transforms: []
    twist: []
    wrench: []
  attached_collision_objects: []
  is_diff: False
error_code: 
  val: -31