Note that update will not be possible if FSX/P3D is installed in a protected folder (e.g. Program Files (x86)) or Program Files (p3Dv4) unless user account has administrative rights (administrator account or “run as administrator” option and UAC is fully disabled (Vista & Windows 7; for Windows 8/10 see here) or modify/write allow permissions have been properly set for the FSX/P3D directory and its folders (see here).