Okay, I'll find my way on C ++, which for me is the language that I do not understand!
You don't need to worry about the C++ languages, you must just be sure the runtimes redistributable, which are part of a standard Windows installation, are correctly installed and not missing/corrupted.
This is not mentioned before the purchase of products (or I have not seen!)
It's not mentioned, for two obvious reason:
1) On a normally installed and normally running Windows system, the runtimes are supposed to be working, and if they are missing, our installer automatically installs them. If they don't work on YOUR system, it's an exception and a problem, not the normal case. Which brings to point #2
2) As clearly explained all over our website ALL our products are available in TRIAL VERSION, which means you are supposed to install, test them and THEN purchase them. The point of offering a Trial version, is that you can check if the product works on YOUR system, so you can check if there are problem with your system configuration and the addons BEFORE purchasing.
The fact to uninstall and reinstall the new will not have to worry about my other scenes or addon?
If with "the new", you mean the correct version of the VC++ runtimes, they shouldn't have any effect on other installed products. In fact, they might even fix problems, even in products that don't have anything to do with FSX.
But again, if you really cannot fix it yourself, we can offer direct support with Teamviewer. Contact me with a PM ( Private Message ) to arrange that.