I was having problems launching a quite new install of PsychoPy3 (2020.2.4post1) on my Windows 10 laptop, where I would click the icon and nothing would happen. It actually launched the first time when it was totally freshly installed, but not after that. I tried clearing the settings, to no avail, then I tried launching from the command prompt:
C:\Program Files\PsychoPy3>python.exe -m psychopy.app.psychopyApp
To my surprise, this launched PsychoPy2 (1.83.04)!! I have an existing installation of PsychoPy2 for running older experiments, so somehow it found that. I had thought that parallel installations should work fine as in the past - they are in different folders.
How can I solve this?