I had this problem with my privacy policy guys, this is how i fixed it:
- On your wordpress dashboard, click on pages, then click on your "advertise here" page.
- Where it says permalink, copy and paste the whole URL, should be something like "yoursite/advertise-here".
- Next, click on the Editor part of the appearance tab on the left hand side.
- On the Right hand side, click on Footer.
- Where it says <a href="/advertise-here">Advertise</a>, delete the "/advertise-here" part, and instead insert what you copied. Should look like this: <a href="yoursitedotcom/advertise-here">Advertise</a>
- click update file
- now try again, hopefully that should work