Very impressed with this airport, during my trial period Lufthansa, Air France and British Airways would show up in the IAB terminal, but now they have disappeared !!! Only a bunch of United Airlines planes, one American and one Delta. What happenned ?
This seems to imply that, traffic was working in Trial, and doesn't work after purchase. This cannot obviously happen: everything in the scenery that might have any effect on AI traffic is the AFCAD, and that one (as the rest of the scenery) surely doesn't change between Trial and full version. NO single file changes when you activate the scenery! Every single file is bit-by-bit identical.
When I use the airport the cast shadow on ground box is automatically unchecked
That's not correct. When you are on an FSDT airport, the cast shadow on ground option is enabled/disabled dynamically depending on the altitude, so it's enabled if you are on ground.
However, this should be a problem only on airports that used a specific kind of (FS8-style) runway lights, which KIAH doesn't use, because it's 100% FSX native and runway lights are 100% custom made, so this should be the usual problem of the airplane cast shadow option. If you are affected by this, you will SEE the AI, but only their lights. If you don't see any AI, not even the lights, this is not the issue.
Please help me in getting WOAI traffic back.
I'm sorry, but I cannot see how this could have anything to do with the airport. The gates are there, and they are all correctly set with proper airline codes, so there's no reason why AI traffic won't go there, and if it doesn't, it's a problem with the AI Traffic package you use.
Have you checked your traffic SCHEDULE in the Traffic.BGL file ? AI don't appear on a certain airport automatically, a proper schedule to depart/arrive on that airport must be present in the Traffic.BGL file so, if you have a problem with it (for example, being in FS9 format, or having a duplicate file), AI won't work. Again, this is entirely unrelated to KIAH.