I just got the MCT-370 door sensor working, after some initial struggles. Mind you, I’m replying over a year after the original post, and I’m using the V3 Smartthings hub, so I’m not sure if the circumstances are different now. Nevertheless, here are my sequence of steps from start to finish, in case anyone in the same boat stumbles upon this thread:
(1) Add a device in the Smartthings mobile app (iOS in my case), and select the “ZigBee Door/Window Sensor” by Ecolink as a starting point.
(2) Go through the wizard, and when it gets to the step to “Remove the battery tab from the sensor,” remove the battery from the MCT-370, then press and hold down the black spike/button while putting the battery back in. Keep it held until the green LED starts glowing.
(3) After a few seconds, it should be paired as a device called “Thing.”
(4) Log into Smartthings via the web, locate and edit the device, and set the type to “Tyco Door/Window Sensor.” While you’re at it, rename the device to something more meaningful than “Thing.”
(5) Reload the mobile app and it should be fully functional, and showing open/close status accordingly.
It’s been working great since; I created an automation to lock my front door whenever the sensor detects closed, and that has been working nicely.
Hope this helps!