Sorry to hear that you are having problems with Firefox.

Can you please try opening the downloaded file from the downloads folder? To do this, please click the little folder next to the downloaded file or right click the file and select Open containing folder.

Is Firefox displaying the usual Open/Save/Cancel dialog, or just saving? If you are not getting the dialog, check whether you need to change the Application preferences for Excel files. Here's how:

Open the Options page using either:

• "3-bar" menu button > Options
• (menu bar) Tools > Options

In the left column, click Applications. This may take several moments to load as Firefox reads from disk.

In the search box above the list of application handling settings, type or paste excel and pause while Firefox filters the list. Do they all still say "Always Ask"? I have attached a screenshot, but you may have different items depending on the type of Excel files you receive.

I've tried that several times. It goes to the File Explorer and when I touch the file to open it goes to Excel but the file doesn't open. The file looks like it has downloaded because the size of the file is around the same size as files that I've downloaded in the past.

It's set to "always ask" and it's been doing that. Once I try to download a file and I tell it "OK" to open in Excel it downloads and jumps to Excel but nothing happens. The file is in the download box under the arrow on the top tool box line. But the files won't open. I've tried to open through File Explorer as well.

Excel doesn't give any error message about the wrong file type or extension or anything -- it just behaves as though you didn't pass it a file name?

Since the problem happens when you launch an xls or xlsx file outside of Firefox, directly from Windows Explorer, its sounds as though a Windows setting might be corrupted.

Have you shut down and restarted Windows since this problem began?

For Office 2003-2010, there is a command line switch to refresh the registry settings for Office programs. https://support.microsoft.com/kb/291288

I'm not familiar with how to do that for Office 2013-2016.

It sounds like this is not a Firefox specific issue. It sounds like it may be in your best interest to contact Microsoft for further assistance on this issue. They can probably provide better assistance with this issue, as it is directly related to their product.

I would recommend running a trustworthy registry scanning tool to see if it can patch the issue or maybe you can even try resetting/reinstalling the Microsoft Office Suite.