Check to make sure that the HDHomeRun has a good network connection, as indicated by the network LED on the device being solid green. The network LED is part of the network port.

If the LED is blinking red or solid red, this indicates that the device does not have a network connection. Try a different network cable and port on your switch/router.

If the LED is blinking green, this indicates that the device has a network connection, but has not received an IP address from your router via DHCP. Make sure that your router is powered on and has its DHCP server enabled. If the router has any access control/allowed devices/MAC filtering function, either the HDHomeRun needs to be on the allowed list, or this function should be disabled.

Make sure your router has multicasting enabled if it has this option. This is needed for the device to be detected on the network.

If using a WiFi client, try instead using a hard-wired client. If the wired client works and the WiFi does not, check the router’s configuration for anything with the word broadcast in it, or anything like wireless partition/isolation/segmentation, and try toggling those options.

If your network is configured to use static IP addresses, check to make sure that the settings (especially the subnet mask) exactly matches that which is defined in the router. Any mismatch, no matter how small, can prevent discovery of the device from working.

If you have more than one router (outside of a mesh system) this creates a network-within-a-network, and you will need to put one of the routers in “Bridge mode”, or have your clients on the same router as the HDHomeRun.

If your router has Access Control enabled, log into it and add the HDHomeRun to the allowed list.

Make sure you are not connected to a VPN. VPNs are isolated from the local network, and will prevent access to the HDHomeRun devices.

If you're using a PC and it has 3rd party anti-virus software installed (Norton, Avast, AVG, McAfee, etc) make sure any local network firewall it provides is disabled.

If your device is using a wireless connection, make sure that you are on the primary 5GHz network and not a 2.4GHz or the guest network.

If using Windows, make sure your settings use “Private Network” as described here: https://support.microsoft.com/en-us/windows/make-a-wi-fi-network-public-or-private-in-windows-0460117d-8d3e-a7ac-f003-7a0da607448d

Android devices using the Google Fi VPN, such some Google Pixel phones, may need some additional settings to allow the HDHomeRun app to work: https://info.hdhomerun.com/info/google_fi_vpn

Make sure you have granted the HDHomeRun app permissions to access your local network. Go to the Settings app → scroll down to “Apps” → “HDHomeRun” → make sure “Local Network” is turned on. If the HDHomeRun app is not listed there, then try deleting/uninstalling the HDHomeRun app and then reinstalling it from the App Store. Be sure to select the option to allow access to the local network, when opening the HDHomeRun app after installation.