In OpenPlant Isometrics Manager CONNECT Edition, the requirement is to add a detailed sketch in isometric. Detail sketches are required in drawings to get the clear details of online components & sometimes others as well.
The below wiki article explain how to attach a detailed sketch.
If above problem still persists, then please create a Service Request and contact the Bentley Product Advantage group. Please include a list of all relevant details to get in depth analysis for a solution or workaround