MOBI files won't work on Kindle PC

Recently I purchased an epack from Sitepoint. I downloaded the the MOBI files but to my disappointment, when I attempted to open them using Kindle PC I get a runtime error. I was hoping somebody could help me resolve this issue. I’ve bought books directly from Amazon and have had no problems at all. I’m wondering if I can only use Kindle PC with books purchased directly from Amazon. I would think it should work either way.

I’ve also created a YouTube Video of what I’m experiencing. I’m hoping somebody can help.

YouTube - Can’t read Sitepoint mobi files with Kindle PC