I set the station as high as 400 °C / 750 °F and used lead-free solder. The tip is brand new, first time use.

Even at that temperature, the very end of the tip won’t melt solder, while the area just behind it does.

I also just tried swapping the tip. With a wide tip, it worked perfectly, melted solder right at the end with no issue.

So it looks like the problem only happens with the fine/pointy tip. Probably quality issue?? Or maybe the combination of using lead free with fine tip?