Hello,

Normally we do not offer support for third party plugins. But i can advice you to double check if you got the right css class and add a !important after the attributes.
Example:

.wpcf7 input[type="text"], .wpcf7 input[type="email"], .wpcf7 textarea {

background-color: #fff !important;
color: #000 !important;
width: 50% !important;
}

Best regards!

Hello,

We recommend plugins that are compatible and work best with our theme. But do not other support as they are some other author’s work. That exclamation mark, is nothing to worry about.

Best regards!

Hello,

There are times that it may take even longer to show a css change. It’s not fault of the custom css box. That happens because your browser has a cached copy of your site and it needs time to take the new preview. So does other CDN over the network.
In these cases, just clear cache to see your changes sooner, or open your site from another browser.
Nice to know you’re ok now.

Best regards!