I downloaded and reinstalled both the 32 & 64 bit VC++ libraries from your link provided but still get the error. So I uninstalled GSX reinstalled the VC++ libraries and reinstalled GSX and still the same error. I currently have GSX installed in to the following location C:\Program Files (x86)\Addon Manager which was the default provided. I have attached a screen shot so that you can see what the install looks like in my computer.
As I've said, this error doesn't have ANYTHING to with GSX or its installation, and it's useless to reinstall GSX or trying to understand if there's something wrong in its installation.
The cause of the problem, which you can confirm by simply googling for that error text, is a problem with your VC++ runtime redistributables, and it might be caused by something that might be entirely unrelated to flight simulation.
Maybe another application you are running has installed the runtimes in the wrong way, so it's preventing the MS installers to update it successfully, possibly because the application is running.
Try to close as many running application as you can, and reinstall the MS runtimes. Both x64 and x86 version.
Another thing to try, is to Uninstall ALL versions of the VC++ 2015 runtimes, restart Windows, then reinstall all of them.