Hello Josh
In your google project and credentials - did you change the values under Authorized Redirect URI? That have be real FQDN's for your Clearpass. Can't use uri's like http://192.168.10.10 which is a common scenario for lab. As a workaround for lab try this:
If you're on a Windows client testing this:
Edit your c:\Windows\System32\drivers\etc\hosts file
Add the local IP of your CP and some valid domain name - like this:
192.168.10.10 myclearpass.yourfakedomain.com
For Mac it's \private\etc\hosts
Note! The domain just have to be resolvable for you - not for google. Of course - in a production scenario you will need a valid FQDN that your guests resolve when accessing Clearpass.
Update your Google project with the complete URI under Credentials -> Authorized Redirect URI ie: http://myclearpass.yourfakedomain.com/your-loginpage-name.php
Also make sure that your Controller now also redirects to the new URI for your guest social login testing :)
Thats it!