There are a few reasons that your Chromecast may be having trouble connecting to your WiFi network. Any one, or a combination of the following, simple fixes could be the cog in your wireless wheels.
If these don't work, then it's possible that you have a faulty unit and may need to take it back to the store.
Factory data reset (FDR)
The first and easiest possible fix is to completely reset your Cc back to its factory defaults. This will not delete any of your app data. All it means is that your Cc number will change (which makes no difference to you or your devices) and you’ll have to go through the setup process again.
Hold down the button on the back of your Cc dongle for at least 25 seconds. Once your TV screen goes blank you can let go and wait for it to clear its memory.
It's also a good idea to try a using different device during your second setup attempt. For example: if you tried to set it up using the Chromecast app on your phone the first time, download the app to your housemate's and try using theirs the second.
Reset your modem/router
Turn your modem and router (often both are part of the same device) off and disconnect from power. Wait around 10 seconds and reconnect power before turning them back on (modem first, router second if you have separate units).
Wait around 30 seconds to 1 minute before trying to connect your Chromecast again.
Use the extender
Your Chromecast (Cc) came with a short HDMI extender cable. This is a stiff cable, a couple of inches long, that will cause your Chromecast to stick out the back of the TV. The purpose of this cable is to give your Cc a little more breathing room to detect WiFi networks.
Televisions are essentially giant shields through which signals have a very difficult time passing. Your Cc needs all the help it can get. Even if this isn't the problem, it's a good idea to use on the off chance it will improve streaming speeds.
Move your router
Along the same vein, if your router is in a distant area of the house, or if it’s at such an angle that it has difficulty getting to your Cc, then it may be time to move it.
Alternatively, you could get a WiFi extender or separate WiFi router to place near the Cc.
Make sure your network operates at 2.4GHz
There are two frequency bands over which WiFi networks operate: 2.4GHz and 5GHz. Chromecasts only work on 2.4GHz.
This can be annoying, but the silver lining is that 2.4GHz is the superior of the two options for a streaming device, thanks to its lower frequency being better at penetrating solid objects.
Go in to your router settings (instructions usually on the under-side of your router) and check what frequency it’s operating on. If it has multiple options, you’ll have to select the 2.4GHz one for your Chromecast.
If your other devices are connected to a 5GHz network you might be able to leave them be, depending on the abilities of your router. Just make sure you tick the option for “Enable guest mode” during the Chromecast setup process.
Update your router's firmware, if needed
When you log in to your router's settings menu, there may be a notification regarding a firmware update. If there is click it. Even if it ends up making no difference to your situation, at the very least it will improve your network security from external threats.
Adjust your router channels
Lastly, most routers come set up to select what wireless channel they run on automatically. This can mean that your network ends up operating on the same channel as your neighbours, which can cause interference.
Go in to your router settings. Instructions of how to do this should be on the underside of your router. If not, try a web search using your router’s brand and model number.
Look for a section called “Wireless” and a subsection called “Channel and SSID”. The names of these menus may vary depending on your router.
Find the “channel” field. If it is set to “Auto”, change it to any numbered option. If the problem continues, change it again until you find a channel with less interference. Alternatively, use a tool like WiFiInfoView to take a look at your surrounding WiFi networks and what channels they run on.
Popular opinion around the web is that Chromecast operates best on channels 1, 6 and 11, although we’ve seen no evidence of a specific channel making a spot of difference. Just make sure that as few of your neighbours as possible use the same channel as you.
This will not only improve Chromecast performance, but WiFi speeds and reliability in general should be better once you make the change.
Original WiFi Router image from Shutterstock