Thank you.
The issue stems from your already having a lib directory in your project, which prevents the pavlovia.org back-end server from linking its own lib directory.
Changing your lib directory to a different name should do the trick.
I am currently working on making that lib error visible to designers, so they can better understand what is going on.
Incidentally, jsPsych version 6.2.0 and 6.3.0 are now available on pavlovia.org, together with the official plugins packaged with the releases, so you do not need to have 6.2.0 in your actual project (I am working on a pavlovia plugin for jsPsych 7, which should be available in the coming days).
Best wishes,
Alain