Attempting to use various Solid Tools (Trim, Subtract, etc) I would receive the following message “One or more of the selected object is either not a solid or is locked. The non-solid/locked obj. will be deselected before this operation is performed”
I searched this and other forums but nothing seems to fit or resolve the issue.
I sort of just figured it out over a bit of time.
My fix was this. Somehow, the two components in question were basically nested components. I am not certain how the same object became nested in the first place. Once I exploded the outer component of both objects leaving the inner (identical) component. The remaining (un-exploded) components allowed me to use the solid tools without error.