Spent the better half of a day tapping and clicking around the internet. Save yourself the headache.. check out https://www.win-acme.com/
It’s a command prompt based LetsEncrypt installer that’s MAGIC. 
Remember to have incoming ports 80 and 441 open or it will fail. Apart from that the instructions are self explanatory.
I’ve attached a screenshot of the interface (well.. a screenshot of their screenshot.. inception)
Pro Tip: Remember to open command prompt as Administrator (right click command prompt) or it may not work. I tried to take a screenshot but .. Mac + remote deskotop = no bueno