I tried all yet, I typed serial correcly (and without spaces)
You haven't.
I run FSX as administrator, but there no happen nothing.
The fact you run FSX as administrator or not, doesn't have any effect on what you are describing. If you ran it as limited permission user, you would get the question "Do you want to activate on this PC", and it will activate, but it might repeat the same question if you launched FSX again.
Instead, if you are not seeing the question, it means you have typed the serial wrong. A common mistake might also be confusing the letter "O" with the number "0".
They must give me any solution, Im a customer more and I paid for your software but I can´t enjoy it.
If you contact me via support email with your Order Number, which is what you normally should do whenever you have a problem with an order, I can send you a .REG file, so you don't have to type the serial. The forum is more suited for general interest question and, since nobody ever had a problem with typing the serial, it's not a problem of the software, otherwise everyone would have it.