Error parsing app package

I just had the same error message while trying to install a downloaded package. While looking into my problem I learned a few things that mich be useful to anyone else coming here.

The problem here could be the application is not able to access the URI addresses.  Even if the individual URLs are available via a browser, the application doesn't think they are valid. In this example I can see the publisher is "myCert" and the URI addresses are http not https. From my quick reading it looks like https and file are supported. no mention of http. Someone reply if they can confirm .appinstaller supports http:

>> Trying to use http without a valid certificate that could have been the problem.

Note:  

The Name, Publisher, Version, ProcessorArchitecture, and ResourceId must match the values in the AppxManifest.xml file specified in the app package Uri.

One can check the details by entering the package URI into one of the many certificate checkers like: "https://ssltools.digicert.com/checker/%22

In my case my firewall was blocking the application. I use Tinywall and it needs every new application to be approved to use the internet. This resulted in "Error parsing app package" rather than some other useful message to inform me what went wrong. Not useful error message.