Custom CSS on Portfolio Pages

Hi. I’ve been using the custom CSS option on my ‘Pages’ to change headline colours/size etc but unfortunately, the Portfolio pages within the theme don’t have the WPBakery Page Builder active (doesn’t seem to show up on those pages).
I’ve tried adding some custom CSS into the theme (across all pages in the ) in the Appearance section but that also doesn’t work.
I also tried to install several plugins so I can add custom CSS to the Portfolio pages and they also don’t work… I’m I missing something or is it just not possible to customise css on the Portfolio pages?

BTW, All I’mm trying to do is increase the size of the h1 headlines on specific portfolio pages. here is one of the pages that I can’t get to work: http://www.productrenders.co.nz/portfolio-item/chairsolutions-2/

Thanks

Ticket