Hi,
Thank you for writing to us.
The auto-discovery issues are usually due to factors external to TuneBlade. In order to verify this, you can install Apple iTunes on the same PC where TuneBlade is running and check if the AirPlay receivers are being discovered.
We've made a short troubleshooting guide on this issue:
The best solution is to add the receiver manually as you've done already. When a receiver is discovered using auto-discovery, it's IP and port are shown in TuneBlade Settings -> Receivers section. Make a note of this, and add the receiver manually using these settings.
Another recommendation to restart the auto-discovery service, instead of rebooting the PC, you can go to Windows services and look for "Bonjour Service", and restart it. At times, re-enabling WiFi does the trick.
Please let us know if you require any further support.
Thanks,
The TuneBlade Team