System error 12002 is a generic network timeout error, it comes from your operating system. It means that -- due to e.g. a firewall blocking traffic between the Inquisit Player on your system and the server or some other connectivity issue -- Inquisit cannot retrieve the files from the server, i.e. the "Unable to open file" error flows from the network timeout.
The error does not indicate any issue with the script itself. I've tested the web demo of the dot probe script I assume you've attempted to run ( https://www.millisecond.com/download/library/v5/dotprobe/genericdotprobe_images/genericdotprobe_images.web
) and I can confirm that it works okay.