More information is needed:
Do you have the User Guide/Manual?
If not, start with the following link:
https://support.google.com/chromecast/answer/6006232?hl=en
All to easy to get carried away with setting up a new "toy" and overlook some requirement, step, or configuration setting.
Uninstall everything and very carefully try again. Read carefully, watch the screens, keep notes.
Watch for some message, pop-up, or other indication that something is not as it should be.
Some specific problem needs to be identified.