We want to implement "Snap-ins chat" in Lightning service console. Please help or suggest required steps.

As an initial set up, we have created snap-ins deployment, mapped Live agent settings and copied "Snap-in code snippets" in VF page. But when we are opening VF page as preview, we are getting below error in Chrome browser console. We have added SF HTTPS domain url in CORS as well. How to resolve this error?

Error message:
Access to Font at 'https://a.sfdcstatic.com/content/dam/www/ocms-backup/system/shared/common/assets/fonts/SalesforceSans/SalesforceSans-Regular.ttf' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access. The response had HTTP status code 404.