You may want to try a reboot of your Android, Chromecast and router. If the content you are casting has an embedded cast icon use that rather than screen casting as it is more reliable.
If the content isn't cast enabled be sure your Android is not running any other apps, turn off any power saving modes.
It's us again. How's it going? Do you still need help? If so, you can also check this support website article to see additional steps and let us know how it goes.
As always, thanks for the help here, JillG and Jeran.