Are you running the newest Adobe Reader DC as was a major update/release because of hundreds of security issues. Suggest uninstalling your and sticking in the new one as have heard some do not update at all : https://fileforum.betanews.com/detail/Adobe-Acrobat-Reader-DC-for-Windows/942951453/1 (do not worry about URL site, used it for 20yrs) I think you then have to sorta let it sit while running it until it figures out it's on Firefox and it has a plugin for that. It will eventually give small icon notice do you want to add this.... Most I know on it.

Please let us know if this solved your issue or if need further assistance.

Well..I did what you suggested with no luck.

And, further, I went to download a report that is usually available as a pdf; there is no pdf option for that report using the Firefox browser. Additionally, in one instance (another web site) the option to "view" a pdf automatically downloaded the pdf file to my desktop without opening to "view".

This lack of functionality is a non-starter.  :-(

Thank you for your suggestion.