Solution
Generally, the "
Add python.exe to Path" option will not be selected by default when installing Python, and it will show a crossed status. Without this option, LabVIEW will display an error message. Please take the follow steps:
1.Reinstall Python and make sure to select the "
Add python.exe to Path" option during installation.

2.After the installation is complete, open the command prompt to install the module as required. An example command is as follows: "
pip2 install opencv-python".