Nav bar not visible

The username/pass don't work for me.

Can you confirm?

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Done. Please check

The Archive Header element is causing the issue - selecting the Site Header replaces the header of your site:
https://docs.generatepress.com/article/block-element-site-header/

Perhaps you meant to select a block element page hero instead?
https://docs.generatepress.com/article/block-element-page-hero/

Ah, thanks Leo! It was a mistake on my part.

Thanks for all your help!

No problem :)