The message doesn't say just that. It also says to download and install the latest Stand-Alone Addon Manager, which you don't seem to have done, because you are still running a previous build of the Couatl.exe program, the current one is 2358.
The difference between the 2356 you are running, and the current 2358 is, precisely, the getRunningMode() function, which communicates to the plugins if the host sim is FSX or P3D.