I’ve been searching through the weeds online for a related post that will address my problem about duplicate content after changing my permalink structure, here’s my problem: About two weeks ago I changed my permalink structure from tegoryname%/%postname% to just %postname%. I then downloaded and setup a plugin called “Advanced Permalinks” that creates 301 redirects for all pages with the old permalink structure to the new permalink structure. It works well and I have no 404 errors. About a week ago I

Source: Topic: Permalink Structure Changed – Duplicate Content Now in Google!! « WordPress.org Forums