How to override social media widget using css

Hello,

I am using social media module. I displayed the widget block "Widgets: addthis-share' block" in footer region.

When I inspect the block element, I see this code:

._5n6j {
    border-radius: 3px;
    height: 20px;
    line-height: 20px;
}

In css injector css rule, I typed the below css:

._5n6j {
    height: 40px;
}

It is not overriding. Can you help?

Thanks.