Press the Windows key + R shortcut to open the Run box. Type firefox -safe-mode and press Enter. Can you provide the steps to replicate your issue?

There are three possible scenarios for right-click menu issues:

(A) The site replaces Firefox's menu with its own

Hold down the Shift key when right-clicking to bypass a site menu.

(B) The site has placed a transparent overlay in front of the video so that the right-click doesn't actually reach the image or video (and therefore that section of the context menu is missing)

There's no built-in workaround for this, but I've learned of an extension designed to work around that, at least for images, not sure about videos: https://addons.mozilla.org/firefox/addon/behind/

Another possibility is using the Media tab of the Page Info dialog. While on the page, you can call that up using either:

• Ctrl+i (for Mac, Command+i)
• right-click a blank area of the page > View Page Info
• (menu bar) Tools > Page Info

When the dialog comes up, click the Media icon at the top to show that panel.

In the scrollable box, find the video and select it. Then use the Save As... button.

Note that many videos are delivered in bits and pieces and can't be saved as a single file this way.

(C) There's a temporary issue where Firefox and your mouse are not communicating

This may require a Windows restart to resolve.