A good method for isolating the source of styles that may be having unwanted effects on your site is to disable folders or selectors until you home in on the style.
Expand the selectors menu in the top left of the interface
Hover over a folder and click the disable icon to disable the entire folder
Or, expand the folder and then click the disable icon for individual selectors to isolate the selector that is hiding your YouTube titles
Once you’ve found that causal selector, re-enable all the others and then check which styles have been applied
I see in your stylesheet that you have set display:none via the Behaviour property group for the following selectors: ‘Fl post title‘ and ‘Fl post meta top‘. Perhaps these selectors are applying to the site more broadly than you intended? I’m not certain these selectors are hiding your video titles however, as I wasn’t able to find the text for your video titles when inspecting the HTML in Chrome. Can you remember one of the titles so I can search for it in the source code?
In your related email you asked how to find selectors, hopefully the above tip about the selectors menu answers that question.