Power steering box elbow

2002 Jimny. I have just bitten the bullet and bought a new elbow for the power steering return pipe that screws into the top of the steering box.  The old one was corroded and a struggle to remove, and the old flange nut threads have picked up and are beyond use.  However, the threads in the steering box look OK if a little shallow. The problem is that I cannot get the new flange nut started in the steering box threads. I am hoping someone has been here before and has some advice.  I don't want to force it and risk ruining my new £50 elbow.  Thank you, fingers crossed.