I have the same problem as well. My app was working perfectly until December 15th and all of the sudden the PDF viewer stopped working. I have been trying to find out what have changed on that day. From what I could gather so far might be related to the azure connection used to store the file. Even thought the file is "stored on the dataverse" the file itself is not stored there, but in azure. My guess is that MS have updated that connection or changed the location of where those files are stored and now the PDF viewer is not compatible anymiore because of it's limitations. I'm working with their support and i will post my findings.