Pulling my hair out with this one.
Finding that SOME but not all documents (usually .docx files) are converting and some are not. When they do not work, the "Generating the PDF" message shows forever. The 'X' icon is also missing in many of those cases UNLESS the previous document worked. In other words, if the first document fails, then the 'X' icon never loads. If the first document works, but the second does not, then the 'X' icon has already been loaded and stays. (See image)
There appears to be no rhyme or reason as to why some documents work and others do not. Some instructors have asked the student to upload the SAME file to another assignment drop-box and it worked!
Version: 3.9.1+ (2020061501.06)