ModuleNotFoundError

[smoothPhysics]

I just succesfully installed GATE version 10.0.1.
"opengate_info" works fine and all tests runned by "opengate_tests" were succesfully completed.
Now i try to run my first simulation in my virtual environment from the installation (opengate_env) and get the following error:
ModuleNotFoundError: No module named 'opengate'

Does anyone had similiar issues when running Gate for the first time?
And more important: How to fix that?

Thanks in advance!