By default, websites you have not already approved cannot install extensions into Firefox. (There is a pre-installed exception for the Mozilla Add-ons site.) The error message drop-down should have a control that lets you make an exception.

Or you can update your extensions from the Add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, above the list, look for a "gear" button and click that, then "Check for Updates".

Or if Firefox has checked and is waiting your approval, there will be an indication next to Available Updates at the bottom of the left column.

Usually a link will appear above at least one updated extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

You can inspect and manage permissions including permissions to install add-ons for the domain in the currently selected tab via these steps:

• Click the "Site Identity Button" (globe/padlock) on the location/address bar
• Click "More Information" to open "Tools > Page Info" with the Security tab selected
• Go to the Permissions tab (Tools > Page Info > Permissions) to check the permissions for the domain in the currently selected tab