Hello,
The second one has to worked for it. Well it’s OK we will help you
Where did you add this Css code in the theme ?
Did you added it to Admin panel >> appearance >> customize >> additional css ?
If not try this one add this Css code in Additional Css then publish and refresh.
.section-heading-wrapper {
display: none;
}
I guess this will help you.
If not send us a screenshot with marks and site URL of your site. it will helps us to find actual issue
Regards,