Hi Alexandra,
Did you share the page only or an entire site? Where are the documents stored which you added in the web part?
In the Highlighted content web part, in the Source dropdown, we select where we want to show content from:
This site, A document library on this site,
This site collection**,** The page library on this site,
Select sites. or All sites.
If your site is connected to a hub site, you will also have an option to select
All sites in the hub. If you shared the page only and the visitors do not have the access to the above-mentioned locations, then the visitors will be unable to see the documents.
If you want visitors to see the documents in Highlighted content web part on the page, then you must share the site.
Thanks,
Neha