Warning message: 2038 No point cloud in ROI

Why did Mech-Center display the warning message “[2038] Mech-Viz: No point cloud in ROI”, even if I have checked that there were point clouds of the workpiece in the 3D ROI?

Please check whether you were using multiple Extract 3D Points in 3D ROI Steps and whether any one of them had no point cloud in the ROI, as this may trigger Mech-Center to display this warning message.