Many thanks pschlute for your response. It prompted me to do a bit more work on problem solving the issue. I gradually de-installed the add on sceneries I have for ZGGG and eventually got back to the default scenery where the AI did appear. So gradually added the add-ons back in. Then I found that in inspecting the add on folders a bit more there were 2 AFCAD files in the folder. One produced by AFCAD 2.1 (Lee Swordy) and the other one called afcad-ZGGG added by the original scenery designer. I removed the AF2 file and my AI have appeared at the new airport. So, problem solved.