It is often easier to fully disable these applications while testing for connection and then reenable and make adjustments later. This is very important as anti-virus applications often have their own firewall and network traffic blockers. If you are running an anti-virus product, such as Norton, you may have to follow a similar process. Apple has provided similar instructions here. In many cases the firewall on your computer may be preventing the devices from communicating. WiFi B & G are not really up to modern networking tasks, so please use an AC or N router. New routers support WiFi AC & N, whereas old ones might only support WiFi B and/or G.
So it’s important not to have your Mac on 5Ghz and Chromecast on 2.4Ghz, or the other way around. Some routers (dual band) have create both a 2.4Ghz and a 5Ghz wireless network. Make sure your Mac and Chromecast are on the same WiFi network, same router, and same router channel. Please disconnect it from its power supply for at least 1 minute, then put it back it. Just unplug it from the power supply for a full reboot.
Just unplug it from the power supply, wait 30 seconds, then plug back in. It might take several minutes for the app to find the device. If you have problems discovering the device, here are some trouble shooting tips that can always help.
Please make sure that your Mac and Chromecast are connected to the same Wi-Fi network.
