First off, if you are getting any error messages like, "would you like to enter your license key to get unlimited access" Then if you have a license key you need to follow the prompts and enter that for it to work.
Otherwise this can happen for many reasons. One being, How many isn't able to make a connection to the internet.
Please go to http://www.example.com and see if you can reach this domain in your internet browser. If you get a DNS error or message about DNS you need to update your DNS server settings.
I prefer to use Google's public dns servers <- click this for more information (opens in new tab)
Then just google search if you do not know how to update your DNS server settings.
Another reason I have seen this happen is 3rd party content filters on the computer. If your DNS is set to google's public dns servers then check if you have a content filter on your machine. If so, contact the filter's admin and get it disabled and re-check the extension.
Another reason could be is your clock on your computer is not set to the right time. We need the correct time on your machine otherwise our authentication process will not work so please check the clock and make sure it is the correct time and if it isn't then make it the correct time.