How to activate an existing virtualenv projects?
Open the command prompt
Go to the project directory, where you created virtual environment
And type the same as error shows, as in my  case it was

File D:\Coding files\Python*recommendation-system\venv\Scripts\activate.ps1* cannot be loaded because running scripts is disabled on this system.

So I typed recommendation-system\venv\Scripts\activate.ps1

And it resolved my problem.
I'm a beginner to Django and Python, and I've never used virtualenv before. However, I do know the exact commands to activate and deactivate virtual environments (online search). However, this learning course takes time and sometimes I need to split the work over 2 days.
When I create a virtualenv today and do some work, I'm unable to access the same virtualenv tomorrow. Even when I navigate to that folder and type in .\venv\Scripts\activate, it says "system cannot find specific path".
How can I open already existing virtual environments and the projects within them? Could it be that I need to end my previous session in a certain way for me to access it the next time?