Convert very large NX Assembly to STEP AP214 produces no step file.
Solution
The reason is often, as in this Use Case, the Load Options Setttings with a value of "Minimally Load - Light Weight Display".
Please re-execute File/Open... and on the bottom left side of this dialog, please select "Fully Load", then hit OK.
Then re-execute the File/Export STEP command.
If your RAM is not sufficient, please also try, inside the "Export to STEP Options" Dialog, in the Advanced TAB, to set this checkbox :
Export Assembly as External References.
Notes and References
Hardware/Software Configuration
Platform: all
OS: n/a
OS Version: n/a
Product: NX
Application: TRANSLATOR
Version: V1899
Function: STEP_AP214
Ref: 001-9687050