Park, thank you for sharing that video! It does appear that the sensor is not working. We can do some quick checks to verify that. Right after you pushed print the bed homed and then rose up to the nozzle. It should stop when the sensor senses the bed. I suggest you attempt to interrupt this process with a piece of white paper. As soon as you press print and the bed homes, place a piece of white paper under the sensor and see if you can get it to respond. That will at least give us some more info to work with. If you are able to trigger the sensor with the white paper, start the process over again, and this time please lay the paper on the print bed and see if it will sense the bed, now with the paper on the bed. If none of that works, then we need to trouble shoot the sensor further (bad cable, loose connection, etc.). If one of those tests do work, we probably just need to replace the sensor as its diodes and may have been poorly aligned during its production. Please let me know what you find out. Thank you for your patience and your willingness to help find the source of the problem! I'll be available all weekend. I don't have any big plans to ring in 2018. Happy New Year BTW!