Looking at the site the first H2 on the home page ( your name ) has been styled using the Elementor Typography settings which overrides what ever is set in the Customizer. This means manually changing those elements to the Default font.
Are there any other typography changes that are not working?
Silly question – do you have the Typography Module activated in Appearance > GeneratePress?
If yes then can you go to Customizer > General and uncheck Cache Dynamic CSS and then clear any browser / server / plugin caches.