The IK Rig of the ZED_Manny skeleton is indeed missing in the project; instead, the one of the UE4 Mannequin’s skeleton is present. This will be reworked in a further release. What may be happening is that the animation blueprint tries to use the retargeter on a skeletal mesh with the wrong skeleton (BP_ZED_Manny uses SK_ZED_Manny and not SK_Mannequin, which is targeted by the IK_Mannequin existing in the project, which you might have used to create the retargeter).
To use the retargeting right now :
Before creating the retargeter, create an IK Rig for ZED_Manny (the skeleton in ZED/Assets/Mannequin/Mesh/ZED_Manny) following the instructions of the documentation in the same way as for your custom mesh
Then, create the retargeter targeting the IK Rig you just created, and continue following the procedure.
If that does not do the trick :
Ensure that AlwaysTickPoseAndRefreshBones is set to “Always Tick Pose and Refresh Bones” on the parent mesh (ZEDManny) in BP_ZED_Manny
Check your retargeter settings about root motion (horizontal/vertical apply)
Ensure that you don’t include the root bone in the “Spine” retargeting chain, but the first bone of the spine