This issue is related to the Firefox: Addon can not be downloaded issue.
To enable automatic updates, you have to whitelist our server in your anti virus / malware software.
The server that the extension update is loaded from and that you should whitelist is extensions.jdownloader.org.
How to whitelist depends on the anti virus solution you're using.
UPDATE: AgileBits, the makers of the 1Password extension have written up a post on how to fix this with the most common anti virus solutions.