How exactly are you doing it? Do you enter the theme’s CSS settings? I just tried again and I’m sending you the screenshot below. But some themes are very problematic and buggy. If done correctly, it will look like the one below. Also, if you can add code in the part of the software, you can try pasting the code with tags?
How strange. I’ve tried it for the third time and it still seems to be working. It must be a different issue related to the theme! Another solution that comes to mind is, if you have access to the tag, you can try adding them again within tags and clearing the cache. Or if the theme gives you access to the HTML code inside the header section, you can try the same there.