Embeds not centering

I have been trying to center the embeds with this theme for days.

The only code that will work is for twitter

.twitter-tweet.twitter-tweet-rendered {
    margin: 0 auto;
}

I still cannot get YouTube to center even with

.my-custom-group-class {
display: flex;
flex-direction: row;
justify-content: center;
}

Are there any other tricks I can use?

The page I need help with: [log in to see the link]