Hello Lauren,
there is a difference between the online and offline version of the experiment. offline it is python code, online it is javascript. PsychoPy “autotranslates” its python code to javascript. This does not always work.
So, when the program ran offline, you still might have to make some adjustements to your script (see Wake Carter’S crib sheet).
The error message tells you that the online progam does not know the variable rep. Therefore it stops.
cheers Jens