Conflicker trojan/virus will block the security sites like McAfee,Microsoft,symantec etc.Kindly try to access these site and try to download the free tools from these sites if your able to access the security sites successfully.kindly reinstall the product(for uninstallation use MCPR tool)
Download the MCPR tool from the following link
McAfee software might not detect an active internet connection due to the following reasons:
Conflict with any other security software
Malware infections in the computer
Unable to connect with McAfee server
Or and this works in a lot of cases the installation gets corrupted and a clean uninstall reinstall fixes that
The method is here reboot after each uninatall ie windows removal method and the MCPR removal tool.