You can try to download and install an extension at a later time if you encounter issues with the Add-ons server. Such an issue can happen if the server is overloaded or isn't working properly for other reasons.

I waited 24 hours and tried again. Still getting the error message.

I will try in 12 hours to see if it works.

Any other ideas?

Thank you.

Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) to see if that has effect.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

A few others users reported this problem when installing from sites that redirect to a different server in the middle of the installation process, such as Yahoo! toolbar and LastPass. Something on their systems stopped the download in that case, but we never got to the bottom of it.