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Error piloting experiment on pavlovia

URL of experiment:

Description of the problem:
I’ve uploaded the experiment from psychopy, and logged into pavlovia to set it to “Piloting”, but I get this error message when I try to run it from psychopy

Unfortunately we encountered the following error:

  • when starting the experiment
  • when opening a session for experiment: Mthirkettle/sc_iat_test
  • when opening a session on the server
  • the experiment status is PILOTING but the pilot token is missing from the URL

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

If i try to pilot it from the pavlovia dashboard instead I get this error message:

Error when preparing to pilot the experiment:

Unable to prepare the pilot URL for this experiment.

If the error persists, contact Pavlovia’s administrator.

This is my first attempt at getting an experiment online, so I’m not sure what’s going wrong or what I should try - the experiment runs fine locally (but i suspect that’s irrelevant).



Thanks @MThirkettle, looking into this now for you.

Hello @MThirkettle,

The issue you report may have to do with the computer you used not being able to get a response from the website we use to get the designer’s IP address (the IP goes into the preparation of the pilot token).
Could I ask you to go to the following URL, from the same computer, and let me know what the answer is?



Thanks for looking into this. That website gives me this message:


I’m doing this at work, inside the university network - not sure if that helps winnow down the trouble, but certainly means i’ve no control over the network settings/ip addresses of the computers here.


Thank you Martin. Can I check with you whether you are still unable to pilot?


Thanks for this, yes, it looks like that problem is fixed now.

I’m getting a different error message

Unfortunately we encountered the following error:

  • ReferenceError: taskFile is not defined

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

But I don’t think that’s connected - sort of expected this one. Am i right in thinking it’s due to this bit of code snippet not working properly in the javascript version?

if (participant % 2) == 1: 
    taskFile = ['blocks_A.xlsx']
elif (participant % 2) == 0:
    taskFile = ['blocks_B.xlsx']
    print("****condition file error****")

If so, could you point me in the right direction for a rewrite?

Thanks again,


@dvbridges: could you look into it?

Hi @MThirkettle, you will need to translate your code component from Python to JS manually. If you open your code component, and select a code type of “Both”, you can translate Python (left) to JS (right). E.g., your JS would look like:

msg1 = '';
taskFile = '';

participant = Number(expInfo['participant'])

if ((participant % 2) === 1) {
    taskFile = ["blocks_A.xlsx"];
} else if ((participant % 2) === 0) {
    taskFile = ["blocks_B.xlsx"];
} else {
    console.log("****condition file error****");

I’m having the same initial issue that was posted here. When I go to the ipify address you posted above, I get the response:

Is there a general solution to this problem? It looks like in the case here, you fixed something internally for a specific user… Thanks so much!

I also get the same “pilot token is missing from the URL” error when trying to pilot from Pavlovia dashboard.

Running 2020.1.3 on macOS 10.14.6, tried with both Safari (ipify says {“ip”:“2001:14bb:430:ee31:7192:91d0:2c81:e610”}) and Chrome ({“ip”:“”}).

This doesn’t happen on my experiments running on version 3.2, just on this test I’m doing on the 2020.1.3. What has changed and why?

Hm okay, update on this: Actually the error disappeared when I put a missing resource file where it should be. I was trying to troubleshoot some “unknown resource” issues and trying to get error messages, but this wasn’t the one I was expecting!

So it’s perhaps a slightly confusing behavior from the system to throw pilot token errors if the problem is actually with the experiment itself.

I also am experiencing a similar issue. Its unclear why I am getting the “pilot token missing” error as I am launching the experiment through clicking the “pilot” button on the experiment dashboard page and there is a pilot token present in the URL.

I checked to see if I had any missing files in my resource folder, which I did. After making sure the necessary files had been added the resource folder, my problem was not fixed and I can’t figure out why I continue to get the “pilot token missing” error.