When I remove the hifiberry Pro hat from the Rpi4 the network can no longer find Volumio although I reflashed the sotware on the Rpi4. Worked fine WITH the hat but now I have a new fancy Dac so don’t need the hat anymore but network does not cooperate. Help
Hi Nobbie49, welcome to Volumio. 
You are saying that simply removing the HAT from a working device installation prevents Volumio appearing on the network?
Are you sure that your RPi hasn’t been assigned a different IP address by your router? Can you see the Volumio hotspot on your mobile?
P.S. Always include your Volumio version when posting for help.