Why will the ATV320 autotune function not work in NST state?

Issue:   
ATV320 will not autotune in NST state
 
Product Line:   
ATV320
 
Environment:  
All
 
Cause:  
Autotune not functioning
 
Resolution:   
Sometimes, the drive's configuration can prevent an Autotune. 
For instance, if the drive’s command channel is from a communication network such as Modbus, then a specific command word order must be sent before performing tuning with the keypad.
1- Power on the drive; ATV320’s state is NST
2- Write CMD = 6; ATV320’s state is RDY
3- Write CMD = 7; ATV320’s state is RDY
4- With the keypad, make “Autotuning” = “Apply Autotuning”; the tune isn’t done
5- Write CMD = 271; ATV320’s state is RDY
6- With the keypad, make “Autotuning” = “Apply Autotuning”; the tune is done
 
Another possibility is when the drive status is NST.
For instance, if the drive is set for 3-wire control and DI1 is not active, the status will be NST, and an Autotune is not allowed.