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.
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
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