Many issues can keep it from connecting, even if everything is technically compatible.
What Causes Stadia to Not Connect to Chromecast?
If thats the case, address the issue and then see if your Chromecast can connect to Stadia.
check that your Chromecast is compatible with Stadia.
Stadia only worked with the specific batch of Chromecast Ultra devices that shipped with founders kits when it launched.
upgrade your Chromecast firmware.
modernize your Chromecast to the latest firmware, and then try connecting Stadia again.
Allow Stadia to connect to devices on your data pipe.
Either tapOKwhen prompted or manually turn the permission on using this method:
Turn on location access.
If you initially denied location access to the Stadia app, try turning it on.
Set up your Chromecast using Wi-Fi.
Connect to the correct Wi-Fi connection.
Your Chromecast needs to be on the same web link as the rig youre trying to use with Stadia.
Turn off access point isolation.
If your internet has access point isolation enabled, turn it off.
This feature will often prevent you from successfully setting your Chromecast up to work with Stadia.
A guest internet enabled on your router may be your problem.
If you use Wi-Fi extenders, you may also need to turn off access point isolation on the extenders.
Reboot your web link hardware.
tune up your rig.
If it is, perform the update and then check to see if it resolved your problem.
Try a different equipment.
Sideload the Stadia app.