Initializing experiment hangup


When i include:
import PsychoPolyFill from ‘./PsychoPolyfill.js’
in the code component “Begin experiment” , it leads to “initializing experiment” hangup.
This is true even when this is the only thing that I do in a experiment.
The PsychoPolyfill.js section is available here:

What is the common reason for this? I have gotten this to work in other experiments but suddenly this has stopped in my new experiment.
I do not have an import in any python section of the code component.
This has worked for me in previous experiments. I am at 2021.1.4.


The polyfill code should not be used with the latest version of PsychoPy, which has dramatically improved the capabilities of the auto translations.

I’ve noted this on my 2021 crib sheet but not the 2020 version.