Migration

I’m trying to migrate my website from https://www.coffswebdesign.com.au/bedheadhaven to https://www.bedheadhaven.com.au. I’m using the Thuliumy theme, which I’ve modified quite a bit. When I went to ‘Settings’ in the administration area and changed the URL to the new one, it put the whole thing in an endless redirecting loop when I try to log in at https://www.coffswebdesign.com.au/bedheadhaven/wp-login.php or https://www.bedheadhaven.com.au/wp-login.php

Now the original site at https://www.coffswebdesign.com.au/bedheadhaven doesn’t work and neither does the new one (it’s just a blank TwentyTen theme with no content, and I can’t log in to change it). I backed up all my previous site first but I’ve tried re-uploading it via FTP several times and it won’t work for either location.

What can I do? At this stage I’m facing the potential loss of a few hundred hours work.