Details
Cannot perform a Boolean operation on a convergent body.
Solution
Toggle off the "Treat Degree 1 Spline as Polyline" under File --> Preferences --> Modeling --> Convergent tab.
Then recreate the Extrude.
Hardware/Software Configuration
Platform: na
OS: n/a
OS Version: n/a
Product: NX
Application: DESIGN
Version: V1872
Function: FEATURE_MODEL
Ref: 002-8507823