Error XToolkitBadContext_Regenerate_OTK Java

Hello everyone!

When I try to regenerate my assembly, an exception is thrown:

My code:

 .....
 Solid assembly = (Solid)asm;
 assembly.Regenerate(null);
} catch (XToolkitBadContext e) {
 session.UIShowMessageDialog("Error XToolkitBadContext: " + e, null);
}

The documentation for the exception says:

"This exception is thrown when there is an error of type PRO_TK_BAD_CONTEXT in a Creo Parametric TOOLKIT function called by PFC."

But how to fix this error is not said.
Does anyone know the reason?
Thanks in advance.

Respectfully!