Error when running experiment

I have recently downloaded PsychoPy and am using for the first time. I created a very simple experiment and upon trying to run it I get the following error message:

Traceback (most recent call last):
File “/Applications/”, line 197, in
File “/Applications/”, line 166, in _run
File “/Applications/”, line 102, in
File “/Applications/”, line 98, in main
File “/Applications/”, line 27, in start_app
AttributeError: ‘NoneType’ object has no attribute ‘MainLoop’

After this the application quits. Can anyone help?

Does your experiment contain any loops? If not, try adding one around your first routine. It can have 1 repetition and no spreadsheet.

What version of PsychoPy are you using?