Hello,
Thanks for sending in your question to the forum and welcome. Make sure that the DWF file is not protected in any way, if it is, it will not be viewable. If that is the case, you will want to create it again in the Desktop product that created it and make sure it's not protected in any way. Note that protection is disabling any functionality for the file, like measure, or password protecting it.
Hope this helps and have a great day.