Try adding !important in the style. I went inline on your p tag and did style=”line-height: 30px !important;” and it worked.
edit: Actually looking closer at the css, you have the style for body with a 1em line-height which is after your p style. Move the p style below the body one and that should fix it. I removed the line-height out of your body style and went to normal just as an fyi. But the body style is overriding your p style for that reason.
Any body styling I try to keep at the very top so everything I style specifically will override that.