From your screenshot it appears that your email template doesn’t include the Heading. This may cause problems with other plugins since that is where the main title appears.
First, check to make sure the heading is set here:
WooCommerce -> Settings -> Emails -> PW Gift Card.
Make sure that Email Heading has “{sender}” in it. The default value is “{sender} sent you a gift card”
If you do not see the Heading bar at all in the email, then you have something (perhaps your Theme) that has removed the Heading from the template completely. You can still show the Sender name in the body of the email though.
We use the built in WooCommerce email template system. To override the email you should copy this file:
/wp-content/plugins/pw-woocommerce-gift-cards/templates/woocommerce/emails/customer-pw-gift-card.php
To here (you may need to create the subfolders if they do not exist in your theme folder):
/wp-content/themes/<your_theme>/woocommerce/emails/customer-pw-gift-card.php
Once the file is in your theme folder, open it up in a text editor and make any changes.