By default, fullPage for Elementor or Gutenberg comes with an empty page template. This means that, while fullPage is enabled on your WordPress site, an empty page with no theme dependency will be loaded. That's why your header or footer does not appear on your site.

If you want to show your header and footer again, you just have to disable the 'Enable Empty Page Template' option. This will load your theme template again. Take into account that after disabling this option you might need to know CSS and JavaScript to change the behavior of the page.

Here are two tutorials that explain how to disable the "Empty Page" option.

Disable "Empty Page Template" on Elementor

Disable "Empty Page Template" on Gutenberg