Every other page is working correctly, AFAIK. For example, "http://example.net/about" displays correctly, but entering "http://example.net" into the address bar eventually resolves to "http://example.net/wordpress" and then gives a 404 error.
In the database, I changed the values for site URL and home URL to be correct.
The page that should be displayed is page_id=6. In the database table for "wp-options", the option for "show_on_front" is set to "page". The option for "page_on_front" is set to 6. (I didn't change these values)
I set permalinks to "plain" (so no permalinks). In the reading options I set the home page to show blog posts (instead of a static page). When I do that, the site url with ?page_id=6 resolves correctly.
If I then change the reading options to use "Home Page" for the front page, When I do that, the site url with ?page_id=6 resolved to the correct page but the site address resolves to "example.net/wordpress" and shows the correct page.
I turn the permalinks on and the site url resolves to "example.net/wordpress" and gives a 404 error.
If I use a different static page for the home page, the same thing happens.