So based on the comments here and a response from Monica I went back and downloaded this program again. I am certain I downloaded the same file as last time (although the name MacX is a little confusing for a Windows program) and this time I was able to install and register without a problem.
However, I have to say it is quite slow in converting videos. For example, for me to convert a 255mb MKV video (40 mins of video) to MP4 it took about 20 minutes.
One of my favorite conversion programs which I have been using, HD Video Converter Factory Pro 2017, is able to convert the same file to MP4 in less than 3 minutes. There is no noticeable difference in quality that I can see. I imagine converting a batch of similar files would take hours using HD Converter Pro.
So, thank you for the opportunity to try this software (twice), but I will go back to the converters I have been using.
BTW I am using Windows 10 Pro.