Go to about:config and check if dom.event.contextmenu.enabled = true.

Do I go into Mozilla Firefox "about:config" if so, where can I find that?

You have not helped since you have not clarified where I can find what you are talking about.

In order to change your Firefox Configuration please do the following:

1. In the address bar, type about:config and press the Enter key.
2. The about:config "This might void your warranty!" warning page may appear.
   Click I accept the risk! to continue to the about:config page.

I went to address and typed in "about:config" and accepted the risks.

There is no line that has dom.event.contextmenu.enabled = true or even "dom.event.contextmenu" as a beginning entry

It goes from dom.composition... to dom.cycle...

HarrisAdmin said

I went to address and typed in "about:config" and accepted the risks. There is no line that has dom.event.contextmenu.enabled = true or even "dom.event.contextmenu" as a beginning entry It goes from dom.composition... to dom.cycle...

Have you scrolled down   .......   ?

Yes, I have scrolled down. The list appears to be in alphabetical order.

HarrisAdmin said

Yes, I have scrolled down. The list appears to be in alphabetical order.

And what happens when you type the name of the preference in the search bar   (right above   'Preference Name')   ?

When search for "dom.content" nothing comes up. It is not in the list.

dom.event...

HarrisAdmin said

When search for "dom.content" nothing comes up. It is not in the list.

The name of the preference is :
dom.event.contextmenu.enabled   .........
Would you try again,   please   ?
(and when you   do   find it :   make sure it's value is set to   true)

I search for dom.event.contextmenu.enabled ...

The status column said "default" The type column said "boolean" The value column said "true"

So if all of the settings are correct, why am I not able to use the features in Dropbox?

Have you tried to contact their support   ?

https://www.dropbox.com/contact

I have contacted Dropbox support and they said it was a browser issue.

One of your add-ons could be the culprit.

Let's try Firefox in Safe Mode : If Firefox is not running : Hold down the Shift key when starting Firefox. If Firefox is running : 3-bar menu => ' ? ' (at the bottom of the dropdown) => 'Restart with Add-ons disabled'. Then OK the restart. A small dialog should appear. Click 'Start in Safe Mode' ( not 'Refresh' !)

See :

https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Any difference   ?
If so, then re-enable your add-ons one by one, till you find the one that cuases the problem