Hey Paz,
if something was wrong with .htaccess, there would normally be a message at the bottom of the “Permalinks” settings page; you can try posting the contents of your .htaccess file here, I will have a look if there’s something missing.
Also, just in case – after changing the permalink pattern to “Post name”, are you accessing the pages/posts by simply refreshing them? You might want to try to go to the “Pages” menu, click on a page to enter the editor, and then click “View Page” from there.
Best,
Andrew / Satori Studio