Please check the system log for reason.
Ex: below log pattern showing successful to playback motion "666_IM_Bird"
10-17 14:28:09.933 9688 9716 D xxx_NuwaCoreObj: +loadMotion:666_IM_Bird
10-17 14:28:09.933 9688 9716 D xxx_NuwaCoreObj: -loadMotion:666_IM_Bird [0]
10-17 14:28:09.934 9688 9716 D xxx_NuwaCoreObj: dur:4.0833335
10-17 14:28:09.934 9688 9716 D xxx_NuwaCoreObj: +play
10-17 14:28:09.934 9688 9716 D xxx_NuwaCoreObj: onStartOfMotionPlay
10-17 14:28:09.934 9688 9716 D xxx_NuwaCoreObj: -play
10-17 14:28:09.934 9688 9716 D xxx_BaseService: send2OneAgent:test_app_1, CMD:[motion, play_start, 666_IM_Bird]
10-17 14:28:09.934 9688 9716 D xxx_KiwiService: --motionStart:666_IM_Bird
10-17 14:28:09.934 9688 9716 D xxx_DispatchService2: -task:motion_start, t:2
10-17 14:28:09.934 9688 9703 D xxx_BaseService: post send2OneAgent:[motion, play_start, 666_IM_Bird], clientid=test_app_1, data=null
10-17 14:28:09.935 14539 14565 D xxx_BaseAgent: proxy Svr cmd:[motion, play_start, 666_IM_Bird], data=null
10-17 14:28:09.935 14539 14565 D xxx_BaseAgent: send2User:[motion, play_start, 666_IM_Bird], data=null
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: internalHandleEvent:[motion, play_start, 666_IM_Bird]
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: >>>
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: >>>
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: >>> 666_IM_Bird
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: >>>
10-17 14:28:09.935 14539 14553 D xxx_KiwiAgent: >>>
Ex: below log pattern showing fail to playback motion "001_P4_Tutorial010"
10-17 14:26:15.654 9688 9716 D xxx_NuwaCoreObj: +loadMotion:001_P4_Tutorial010
10-17 14:26:15.782 9688 9688 D xxx_OverlapWindowObj: KiWiService msg=6001
10-17 14:26:16.367 9688 9716 D xxx_NuwaCoreObj: -loadMotion:fail !!!!!!!! 001_P4_Tutorial010
10-17 14:26:16.368 9688 9716 E xxx_KiwiService: --motionStart(001_P4_Tutorial010) error!, mRobotController:com.nuwarobotics.service.NuwaCoreObj@108a224
10-17 14:26:16.368 9688 9716 D xxx_BaseService: send2OneAgent:test_app_1, CMD:[motion, motion_error, 001_P4_Tutorial010, path:default]
10-17 14:26:16.368 9688 9716 D xxx_DispatchService2: -task:motion_start_fadein, t:815
10-17 14:26:16.368 9688 9703 D xxx_BaseService: post send2OneAgent:[motion, motion_error, 001_P4_Tutorial010, path:default], clientid=test_app_1, data=null
10-17 14:26:16.368 14539 14565 D xxx_BaseAgent: proxy Svr cmd:[motion, motion_error, 001_P4_Tutorial010, path:default], data=null
10-17 14:26:16.369 14539 14565 D xxx_BaseAgent: send2User:[motion, motion_error, 001_P4_Tutorial010, path:default], data=null
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: internalHandleEvent:[motion, motion_error, 001_P4_Tutorial010, path:default]
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: !!!
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: !!!
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: !!! 001_P4_Tutorial010, path:default
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: !!!
10-17 14:26:16.369 14539 14553 D xxx_KiwiAgent: !!!
If log shows pattern like "loadMotion:fail !!!!!!!! 001_P4_Tutorial010", it means the motion resource is not existed in the device for sure.