4D Technologies, the makers of CADLearning, stopped generating DVDs back in 2016. We continued to authorize the previously sold DVDs for as long as we could. In 2018 we lost access to the technology used to authorize due to numerous Windows security updates.
Unfortunately, this means we can no longer support the DVDs or our offline content in any way, they are retired products. We would be happy to offer a free trial of our subscription service to former DVD owners who are interested.
If you own a DVD, you can install it, watch the permitted number of videos prior to the required authorization, then uninstall. When you reinstall, you will once again have access to the allowed number of lessons. You can do thus as many times as you would like. Although we realize this is not the intended experience, it does allow you to continue getting some use from the DVD.