Hi Brett,
I'm Sumit, here to answer your query at the Microsoft Community.
Apologies for any inconvenience you are experiencing. We are happy to help you.
This usually means a network issue. Are both of the Macs on 2.4 Ghz or 5Ghz WiFI?
For the Windows computer,
Please ensure the following services are running:
Function Discovery Provider Host
Function Discovery Resource Publication
SSDP Discovery
UPnP Device Host
Please try using IP Adress and let me know if it works or not instead of Hostname.
I look forward to your response and am eager to collaborate until we find a solution.