After importing certain newer driver packages into the Software Catalogue, some of these packages return errors on Package Server for downloads.
In the agent logs on the Package Servers, you could see it attempting to download from the Notification Server package share with a https URL. When this URL was pasted into a browser on the Package Server, the following error was received:
HTTP 500.19 - Internal Server Error
This requested page cannot be accessed because the related configuration data for the page is invalid.
The configuration file mentioned showed there was a "web.config" file in the package folder.
ITMS 8.x
The driver manufacturer had included a "web.config" file in the driver pack.
Remove the "web.config" file from the package and then the Package Server should be then able to download the package successfully.