TC does not find our own Python package

We have installed our own package, pycsp, using the Python instance installed with TestComplete from the command prompt. Using that Python instance from pyCharm IDE, we have no problem importing and using that package. Doing the same from TestComplete (see below), a message says there is no such module (see attachment). Why is that? SmartBear support suggested adding paths to sys.path but it seems to contain the neccessary paths already (when we print(sys.path) from pyCharm; when we try to Log.Message(sys.path) in TestComplete it shows an empty string).  

from pycsp.client import logon

def LogOnNOff():

sess = logon(host='localhost', username='admin', password='admin2')

sess.Close()