Simple Monsters has two versions; 32-bit 64-bit. Please check that you have installed the correct version for your DAW.
Most DAWs are now 64-bit. If you install the 32-bit version, it may not appear in your DAW.
You will have been sent links to both versions when you completed your purchase. You will have these links in an email, or on the ‘Downloads’ section of your account when logged in at krotosudio.com
For Pro Tools 10, older versions of Ableton Live and Reaper, please install the 32-bit version.
In some DAWs Simple Monsters will appear in the plugin list under ‘Other’ e.g. in Pro Tools. Please check this menu to find your plugin.