There can be several factors that can cause recordings not to retrieve the correct CSS style of your page, like:
Your website could be in a localhost environment, an intranet, or within a VPN network. In order to function properly, Smartlook has to be installed on an entirely public website so all the data can be retrieved through a proxy to our servers.
The recording is too short (i.e., it ends after one second) and the connection was not established, meaning the CSS style of your page wasn’t retrieved.
Your website has dynamic CSS. Learn more here.
You might have a firewall blocking the Smartlook proxies. Check your web security settings and make sure you have the header access-control-allow-origin:* enabled.