Whilst working in an assembly, the user encounters a problem with a 3D sketch which appears like it is in editable, with a "GoTo" Icon in the pathfinder. However, once in the 3D Sketch, it is not usable or editable, and there seems no way to close the sketch.
SolutionPlease try following:
1) In PathFinder, right-click on the Sketch -> "Edit Definition" to enter Sketch
2) Press the "Save" Icon
3) Close Assembly - without saving.
After re-opening hopefully you will find that the problem is cleared and the sketch should behave as usual.