Many X-Plane aircraft and addons use Microsoft C ++ Redistributables, specifically, the 64 Bit versions. While these redistributables do belong to Windows, they are not always installed by default. They must be subsequently installed.
Download links to the most common C ++ 64bit Redistributables:
Once downloaded, ensure you install each redistributable one by one. Even if a redistributable appears installed, we recommend attempting to install it again as sometimes libraries may be broken or corrupted. The installer will automatically repair any of these issues.
All other C ++ redistributables can be found here. We generally find C ++ 64bit 2017 is important. In addition to C ++ redistributables, .NET version 3.5 and 4.6 or higher are sometimes required for some addons. Java Runtimes may also be necessary.
You can find further information about this in our X-Plane 11 Forum.