I don’t think that ever worked for me. I just ended up installing a really old version (1.5 or something) to test pingbacks.
Just to confirm – did you add ‘/trackback/’ at the end of URL to get pingbacks?
I’m having a similar problem – I’m running two wordpress servers (running 3.8.1) and pingbacks just don’t show up between each other when I test.
My I know which version are you running please?
