I like fine tips they work great but a blunter tip may get better contact, I tend to have to wet my soldering tip a lot with a quick blob of fresh solder to get good heat contact with my fine tip. Stupid question but is it rosin cored solder? Maybe there isn't enough flux in it? Could try a neutral paste flux or something more aggressive if you clean the joint afterwards. Also make sure you're heating the board up well, lead free solders tend to need a higher temperature, it may not be flowing right because the PCB trace isn't heating well.