Fixed. I don't understand how this happened, but there was a typo in one of the files. What's really strange is that this should have caused problems many days ago.
Because browsers cache libraries, you may have to clear out old copies of the GlowScript software. For example, on Chrome you click on the vertical line of 3 dots at the upper right, choose More tools > Clear browsing data and choose "Cached images and files".
Thank you so much for reporting this.
Bruce