From the FAQ:
Q: I'm experiencing one of the following symptoms:
After selecting a software version, everything grays out and freezes.
I'm receiving the popup message "ERROR. Please check your internet connection."
I'm receiving an error message in the status bar.
A: This is your local connection issue, and can have a number of root causes:
You have modified your HOSTS file. Please remove the following two lines.
0.0.0.0 aa.online-metrix.net
0.0.0.0 c.bing.com
You have installed software that prevents scripts from modifying secure websites, such as certain adblockers, firewalls, privacy tools or similar security related software.
You have disabled TLS 1.2 in your internet settings. You can enable it again in the control panel in the Internet Options category.
In rare cases, starting the tool as administrator can resolve the issue.
In rare cases, installing the latest Windows updates, or updating Internet Explorer or the .NET framework to the latest version can resolve the issue.