'mlagents-learn' is not recognized as an internal or external command, operable program or batch fil

I have been successfully using mlagents for training my projects for several months. But from today I cannot run the "mlagents-learn" without getting this error. Last time I ran this was yesterday night, which was successfully completed without any errors. I copied the 'venv' folder which consist of the python virtual environment and all the libraries to an external hard disk. This was the only different thing I did among the other usual things. I had several copies with this virtual environment folder with several different projects but nothing work now.

Please help!!

 

You'll need to recreate the virtual environment, you can't just drag and drop it because it breaks the activate scripts.