First off, I changed the Natural Gas orifice to a factory ordered LP orifice, I am not just trying to hook up a LP line to a natural gas dryer without setting the dryer up correctly for LP.
My problem is that the female end LP line, professionally installed, does not fit my dryer male connection.
The fitting is so close, it feels like it will thread but just doesn't.
I am seeing stuff online about a flare end to a threaded end
Is there anything I am doing wrong, or is my dryer female not the 3/8" I am thinking it is?
The instructions for my dryer says it is 3/8":
I added some images to assist with my question: