403 Forbidden nginx error when piloting jsPsych 7.3.4

jsPsych version (e.g. 7.3.4): I have recently tried to set up a new experiment on Pavlovia running the most recent version of jsPsych. The experiment runs fine in the browser and I have added the pavlovia-2022.1.1.js plugin and the the pavlovia_init and the pavlovia_finish commands to the timeline but I get a 403 Forbidden nginx error when I try to pilot the experiment. I have reproduced the Simple Reaction Time [jsPsych 7.x] experiment to test whether I can get this running and this also gives me a 403 Forbidden nginx error when I try to pilot the experiment. I have set the experiment back to inactive and then back to pilot, I have cleaned out my browser cache, I have checked all the path dependencies (and as I say I can get the jsPsych script to run on my computer) but still having no joy. I can run some experiments that I have set-up previously but nothing new. Not sure what to try next.