Windows 10 Pro 64bit (Version : 21H1) (AMD Ryzen 9 5950X 16-Core Processor 3.4GHz), 64Gb Memory, 1Tb ssd
Roon v1.8 (build 831) stable (64bit)
Matrix X-SABRE Pro(Mqa)
Somtimes No audio devices in roon app.
Not always, But very frequently.
When It happens, I reboot my PC. Then It’s okay.
I think It happens aound 2~3months ago.
Hey @HoJun_Kim thank you for bringing this to our attention, so sorry for the trouble!
Have you tried rebooting your router, Core, and audio devices by unplugging them, powering them off for a few minutes, plugging them back in and turning them back on? Is there any permanent change after rebooting all devices?
Do you have any firewall or antivirus enabled on your Core machine? Since you are using a Windows PC, I would verify that both Roon.exe and RAATServer.exe have been added as exceptions to your Windows firewall.
You can use these instructions to add the exceptions and the executables themselves would be located in your Database Location/Application folder path.
I would also add these exceptions to any Antivirus or other Firewall blocking applications you may have and ensure that you connected to your network via a Private network, not a Public one, see this guide for more information.
Thanks! 
