Here's some things to try!
- Typing chrome://restart into your address bar and hit enter
- Unplug and plug back in your Chromecast
- Make sure your router has Multicast and SSDP enabled
- Restart your router by unplugging it and plugging it back in
- If you're currently powering your Chromecast from the TV's USB port, try using the wall adaptor. Some TVs don't give the Chromecast enough power which can lead to issues.
As well, some anti-virus programs stop apps likes ours (but not Youtube or Netflix) from communicating properly (especially AVG antivirus!), try disabling any anti-virus programs that you run and rebooting your computer!