Hi Jayne...
The error could be cause by a number items that might need some additional research (need a MicroFocus license, network connection timeout, etc.), so it would best to open a ticket so that we can explore further. As far as support for Windows 2016 server on ACR 4.8 goes, the QA team can do a test to see if ACR runs on the Windows 16, however, any certification for Windows 2016 server would only be supported on newer versions of ACR (i.e. ACR 9.2).