WordPress is giving me 404 page not found for all pages except the homepage

.htaccess is a hidden file, so you must set all files as visible in your ftp.

I suggest you return your permalink structure to default ( ?p=ID ) so you ensure that .htaccess is the problem.

After that, you could simply set "month and name" structure again, and see if it works.

PS: Have you upgraded to 3.1? I've seen some people with plugin issues in this case.

Basically the .htaccess file should exists and the httpd.conf should be correct.

In my case, I changed the file /etc/apache2/apache2.conf in section:

<Directory "/var/www/html">

Line changed is:

AllowOverride None

to

AllowOverride All

And restart the web server with

systemctl restart apache2