Details
Cannot create an assembly feature if the component has multi-bodies.
Solution
Open the part, right mouse click on the Design Body which will be used
by the assembly feature and select 'Activate Assembly Body'. Once activated,
you should be able to place an assembly feature on this component for that
body.
Notes and References
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: 1064
Product: SOLID_EDGE
Application: ASSEMBLY
Version: V108MP12
Function: FEATURES
Ref: 001-9162357