Problem with embed and stuff

The thing is I have a website with this theme and it works perfect. Im creating a new website and I installed the same theme. However, when I try to use the youtube channel for embed a youtube channel on my homepage it doesnt work but the same thing its working in the first website.
The weird part is that when I put the code for the embedding it works in the second site when I paste it on a regular page. It is not working in the front page.

Plus, for example, in the first site i see the option Custom CSS, and in the second site it is not showing up.

Im going crazy about it.!