Hi @Steve1 Steve,
Welcome to the Forum. There are many helpful enthusiasts here to help along with the Arylic Team.
Assuming your PC is Windows, have a look at this post and try the UPnP Analyser.
This will at least establish if it is a Network Issue.
After this has been established then I will think of something to check iTunes on PC (this is maybe/probably using Airplay Service).
Regards, Kevin