Error message on Pavlovia since last platform update

This evening I noticed that any new projects I upload on Pavlovia yield the following error message when trying to run them:

Unfortunately we encountered an error:

  • when starting the experiment
  • when configuring PsychoJS for the experiment
  • missing psychoJsManager block in configuration

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

I know it’s not a problem of one specific experiment, because then I created a dummy project with only meaningless plain text and key presses just to see what happened and it also crashes straight away when launching it (here’s the link:

This seems to have coincided with the recent update to the platform which I noticed happened sometime today.

At least if I try to update the experiments I had uploaded until yesterday by syncing them, those still work fine, but I don’t seem to be able to get anything brand new to work. I would really appreciate it if someone could check if the recent update to Pavlovia has resulted in any bugs.

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There has been a fair bit of work on Pavlovia over the last week - we’re getting ready to release a new version with store/docs and hooks for further control over a running experiment - I’ll check whether any of the preparatory changes might have caused this.


OK, yes, Alain knows the cause and it should be fixed very very soon

Hello Sebastian,

As you correctly guessed, the issue stemmed from our recent update to both the Pavlovia server and the PsychoJs library, and had to do with backward compatibility when creating new projects.
I have just fixed it. As far as I can scertain, your test experiment is working just fine.


Thanks a lot! :slight_smile:

Yes, it’s all working fine now. Thank you!

Hi everyone, unfortunately the same problem appears also on lab.js projects:
I got the same message for a new project, originating from the labjs-pavlovia plugin 3.0.0 script. The old projects run just fine.

Thanks for any help!

Hi, I’m also having this same issue still with new projects.

Hello @MTan,

Could you give me the URL of your experiment so I can look into it?


Same issue with lab.js integration - not sure if this issue is on the lab.js side or the pavlovia side.

URL of task:

Hi Alain,

The URL is Thanks!

Hello @MTan and @dgfitch,

I can confirm that the issue has been fixed. Your experiments are now running fine, as far as I can tell.
@MTan: you are using a very, very old version of the library and I would strongly encourage you to upgrade to a more recent version, e.g. 3.1.3
Many apologies for the interruption!
Best wishes,


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I’m running into the same issue using jsPsych. My experiments prior to the update work fine
(e.g., but an essentially identical experiment post-update
(e.g., is throwing the following error:

[jspsych-pavlovia plugin 3.0.6] Error

  • when configuring the plugin
  • missing psychoJsManager block in configuration

After reading this thread, I thought maybe the issue was my use of an old jspsych-pavlovia plugin (3.0.0), but updating it to 3.0.6 resulted in the same error. Hopefully the fix is similar to what worked for the other plugins.

Thanks for any help you’re able to provide!

Hello everyone,

I also encountered the problem of jsPsych not working properly with recently created experiments. Old experiments work totally fine, but a new one that is nearly identical does not. I also tested it with a simple dummy project ( ), and by updating the pavlovia plugin from 3.0.0 to both either 3.0.6 or 3.1.3.

Both replica and dummy experiment result in the folling error (on pavlovia 3.1.3):

[jspsych-pavlovia plugin 3.0.6] Error

  • when configuring the plugin
  • missing psychoJsManager block in configuration

i also attached the error report generated by the firefox console, perhaps there is some information for you in there.

Thanks for any help!



Link to the still working old experiment:

Hello @vanhedger87 and @valentin,

The issue has been fixed and your experiments are working fine again, as far as I can ascertain.
Many apologies for the trouble! The recent update to the server was a major one (new back-end, new API, new GUI) and a few issues slipped through the cracks.
Best wishes,


Awesome, thanks for the quick work! One minor thing i noticed: some of my new experiments seem to run only on pavlovia 3.0.6, others only on 3.1.3 (just if you have the time to look into it, i don’t mind running them on different builds). Thanks again, especially for caring also about jsPsych related issues!

Thanks for the quick work on this, Alain! I really appreciate it.

Hello-- I am also experiencing this error with an experiment that I just newly uploaded to Pavlovia ( )
Does this error have to be fixed manually? I am using jsPsych to do this …

Hello @davidjohnbaker1,

You are using a very old version of the library, 3.0.0, which explains why my fix did not solve your issue.
I’ve just retrofitted 3.0.0 and your experiment is running again.
Best wishes,


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