What's the trick to caching an image entirely in ArcGIS Pro?

Question

I have created a map service using ArcGIS/ArcMap (10.4.1).  I can prepare it for caching, but the last one took almost 5-days to run, so this time I am hoping to do it entirely in ArcGIS Pro instead.  I would like to cache this image and then use it in Portal.  I have already done smaller ones...this one is slightly larger.  The process usually does work well.

I have created a link to ArcGIS for Server in ArcGIS Pro, but now when I try to add the map service that I would like to cache (using the Manage Map Server Cache Tiles tool) I get an error (000732: Dataset does not exist or is not supported).  I can still add the same map service using the exact same tool in ArcGIS though.

Is there a trick to this that I'm not quite grasping?  Perhaps I need to use a slightly different path?  Has anyone else managed to use ArcGIS Pro to cache an image for use in Portal?

Thanks

MarkHotz · Answer

UPDATE - I have managed to make a connection between ArcGIS Pro and our GIS server (the only thing I did since the last error was to reboot), and I can now add a map service that I would like to cache (I decided to do this in Model Builder as I find that it is better at displaying progress).  However, now when I try to initiate the process I simply get an error:

This is particularly frustrating because I am now processing that very same cache with that same map service using the same "Manage Map Server Cache Tiles" tool in ArcCatalog.  It's sort of a shame because I would like very much to see if ArcGIS Pro can do this faster than ArcGIS Desktop.