After further researching and looking into the network traffic it seems that when the Hub is trying to GET the Request URL for the layers on our open data site, it is not "getting" the entire URL. The layer ID is dropped (e.g. instead of https://opendata.arcgis.com/api/v3/datasets/1bc60d61f55644dc9320624a8fbea521_0 being the Request URL our HUB site is trying to GET https://opendata.arcgis.com/api/v3/datasets/1bc60d61f55644dc9320624a8fbea521 )
Which creates the first resulting in the "404 Not Found" error. The additional error is a "500 Internal Server Error" when you click on the open data download icon and an API Error message instead of being able to download the data.
I have been able to test this with another Open Data site on which our GIS data is accessible. Our site gets the API error but on the other site I can download the same data from the same feature services without issue.
How does this get resolved?