Reminds me my first tank removal. After plugging the fuel line back it didn't start. Wondering what's wrong I inspected the quick connector and saw a little leak. So I unplugged it and plugged it back. It was like a little boy peeing. I had a little closer look at the thing and discovered it wasn't plugged in properly. It needed much more force to plug in than I applied initially.

 

Everything everybody has suggested has been tried and still has failed.

 

FWIW, if anyone goes replacing that o-ring, I would imagine H-D spec'd a Viton o-ring since it's in direct contact with fuel.

 

You need to relieve the fuel system pressure, pull the fuel pump fuse, crank it over for a few seconds, that will relieve the pressure, you can then remove and replace the QD without damaging the o-ring, or spraying fuel everywhere.