I see in the front-end that your Body's Font Family in Theme Options > Typography is Open Sans and that is what the V2 Headline is using if it is set to Inherit. To change the font, first, you will need to setup a font in the Font Manager. If you're not familiar with the usage, please see https://theme.co/apex/forum/t/font-manager/101
Once you have a font setup, it will be able to select the font in the Font Family option of the Headline element.
You're using Francois One for your Headings Font in Theme Options > Typography. This is the font that is being used by the Classic Custom Headline.
If what I described is already setup in the back-end but not taking effect in the front-end, the issue could be a result of caching. If you're using a caching plugin, please clear all caches including your browser cache then check again if the issue persist. Also test in other browsers and incognito mode.