I solved my problem - hopefully this can help others.
I found a link from Microsoft which I followed all directions carefully and it worked.
For me it seems that I had two issues - 1. My UAC was off and 2. My PC Region was listed as United States which is wrong for me as I am in Canada.
Here is the link…
https://flightsimulator.zendesk.com/hc/en-us/articles/360016366680-Error-message-Purchase-failed-