Custom CSS and Override templates not working

Hi. I reached out in the comments section on CodeCanyon. I have purchased this product but you pointed me to the presale section on this forum so I’ll post the issue here:

I am trying to add “margin-bottom: 15px” to the “p” tag on the default template and I have tried added to the Custom CSS section as well as adding to the “email-header.php” template file which I have then uploaded to the “woocommerce-email-template-customizer” directory in my active theme.

However, when the email is received there is no reference to the selector I have added when I view the raw source of the email.

The reason I need to get this added is there is no spacing between paragraph breaks so it looks really messy and is difficult to read.

If you require any further information please let me know.