It could be as simple as running FS in Admin mode to allow the changes to be made to the associated file. UAC doing its job can make ours a pain.
It could be a layer issue where his change is not high enough but he said he checked that, or not properly set to geo-location but if its a modified stock airport it should be set, or most likely as scruffyduck Jon said, scenery complexity. If its not that and it was a custom or library object, it could be associated textures arent there or in incorrect formatting.
Since its been a number of days since the last communication, I am willing to be he has tried to get here, but the DNS park is preventing him from doing so.