HUE Animation is asking me for an ‘offline key’; what does that mean?

HUE Animation is asking me for an ‘offline key’; what does that mean?

If the software requests your offline key, it means it’s having trouble reaching our activation server. This may be due to network problems, antivirus software or a proxy service.

Please use our offline key form on a computer with Internet access to instantly generate your offline key, or check this link for detailed instructions.