Right-click the ADDON MANAGER folder, select properties, and give FULL control permission to your user name. Run "Couatl_Updater" and finish the process then run "Couatl_Updater2" and let it finish again.
That's exactly what the installer does: it gives explicit permission to ALL members or the "Users" group to the whole Addon Manager folder so, normally it shouldn't be required. But of course, if it works for some, it won't do any harm.