Sketched Opening has no sketching plane
A 2D sketched opening (SP3D opening or SM3D opening) has been detected as missing its sketching plane input (previously defined or selected by the user when modeling the opening).
The 2D sketched opening cannot be edited. In addition, copying this opening might introduce issues as the sketching plane is missing.
What You Should Do
A new sketching plane needs to be set by editing the opening.
Open the model.
Edit the opening.
Set a new sketching plane.
Save the session.