Hong Kong Int airport (new) addon scenery error

If you installed it properly it should show up in settings/scenery as the top box checked.
See if it's like that.

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1. Extract the zip into your main FS2004 Addon Scenery folder, or into a temporary folder, and then move it there, which ever method you prefer.
I use the temp and drag and drop.

2. Start up FS2004 and when the welcome screen, or initial menu comes on, select settings, then click on Scenery Library, and Add Area. Find the Addon Scenery folder and open it, then find the XXXX folder and click on it. The name XXXX should now appear in the title window, then click OK. Then you will see XXXX at the top of your scenery library list, and click the OK tab at the bottom.

3. That's it! You must first exit FS2004, and when you restart it your scenery will be there. It is not necessary to use the Addon Scenery option to locate this scenery, simply go to the airport in FS.
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Thanks for your response. Yes, I activated the scenery in the scenery library and the scenery folder is still there. I have done many addones, none like this. I want to get back to the default FS2004. Is there a way. Thanks.

Check out this post to find the default AFCAD.

https://forum.flyawaysimulation.com/forum/topic/11845/here-is-complete-list-of-what-is-on-each-fs9-disk/

You might be able to find a replacement AFCAD here, not default though.
https://flyawaysimulation.com/downloads/112/fs2004-afcad-files/

Be sure to back up a folder before you add anything new or delete any default item.

Good luck with it.

 Neurazte sa ale aby to nebola banálna chyba, že máte málo  MB.