My brother has a 2001 Maxima and recently replaced the shifter solenoid pack , (the car would not shift into 3rd gear). This may or may not have been his problem. Now that he has completed this the shift lever is not responding. It will move to all settings, but nothing happens. I'm not sure what he may have done wrong, but obviously he has. Any thoughts or ideas?

 

There are several possibilities. Maybe the wire harness for the solenoids is not plugged on all the way.

Maybe one of the line pressure ball bearings and/or spring popped out without being noticed. See pages 314 and on, especially 316.
http://boredmder.com/FSMs/Nissan/Maxima/2003/AT.pdf

I remember reading that one person replaced solenoids and the trans didn't shift. He reseated the solenoids.