And, as I told previously, CYVR is working well with no trouble, and CYVR is in the same folder that KIAH, so how it is possible CYVR gets permission and KIAH not???
After looking at your log, I don't understand why you also thought you had a permission issue to begin with, since nothing in your log shows that something remotely similar to what's happening to the user altamuro is happening to you.
Your log doesn't show ANY error access to the C:\ProgramData folder, so no, you don't have any permission issues.
And, your log doesn't show that GSX is regenerating its cache at each start. Maybe you saw it regenerating its cache several times, and assumed it's *always* regenerating, but it's not. At least it didn't in the session your log was referred to.
If you just installed a new scenery, it's normal that GSX would regenerate its cache. And, if you have both FSX and P3D installed on the same system, it's normal that you will see a cache regeneration each time you switch from a sim to another, because the GSX cache location is shared too. We plan to fix this in a future GSX release, but there are no issues if it's happening, just a minor annoyance.
Instead, your log shows this:
Loading addon KIAH
Addon KIAH not installed or missing one or more files, skipping
No wonder KIAH doesn't work, and CYVR and JFK2 do. It seems you haven't installed KIAH. The scenery itself HAS an entry on the Scenery Library, but its Couatl code is just not there. Which shouldn't normally happen because, of course, the KIAH installer installs everything that is needed by the scenery to work.
You should have a file named __INIT__.PYE in the FSX\fsdreamteam\Couatl\KIAH folder. This is supposed to be put there by the KIAH installer.
Of course, if you Uninstalled something while testing, and replied YES to the question "Do you want to remove the Couatl scripting engine", everything related to Couatl would be removed and, as the message also warns, every other product requiring it would stop to work, and this includes KIAH. You probably did this when uninstalling something else, like GSX for example, because it would LEAVE your KIAH area (obviously, GSX doesn't remove the KIAH scenery area) but if you told it to remove everything related to Couatl, it would remove all the KIAH Couatl files.
So, to fix your problem, you will simply have to install KIAH.