Code snippet language is in HTML, but not rendering in browser

**Operating System**: Windows

**DocFX Version Used**: 2.43.5.0

**Template used**: default

**Steps to Reproduce**:

In my MD content I have some code snippets tagged with the programming language.

In the HTML output, I see the appropriate pre and code tags and also the class attribute:
```

 ... 

**Expected Behavior**:
When I view the HTML page in a browser, I would expect to see the code example displayed along with the name of the programming language. Similar to [this](https://docs.microsoft.com/en-us/azure/active-directory/develop/msal-net-initializing-client-applications#initializing-a-public-client-application-from-code).

**Actual Behavior**:
The code example is rendering in the browser, but the name of the programming language is not being displayed.

I'm maintaining a site that someone else set up. There are a lot of code samples in the content, but I can't see the programming language for any of them. Any help would be appreciated. Thanks.