.htaccess file is a bit dodgy.
Mine was set to 660, which is all enough, and it should be writable by wordpress.
Then suddenly, it became not. I couldn’t update .htaccess file through wordpress nor cpanel. After save, it just went back to the original in cpanel, and wordpress says it’s not writable.
So I deleted that file, then created another one. Same 660. This time everything works again.
Have you set up the correct address in your options? It should be the blog address, not your website root address.