Failed to fetch error when uploading participant's data at the end of the experiment

Online experiments
1

Hi,

one of my participants got the following error at the end of the experiment.

"Unfortunately we encountered the following error:

  • when uploading participant’s results for experiment …

  • TypeError: Failed to fetch

Try to run the experiment again. If the error persists, contact the experiment designer."

Incomplete data was not saved either. Any idea why?

Thanks!