Do you have other device handlers in your account? If you’re running into the stale DTH issue, any unused device handler can be blocking it. Just to ensure that it isn’t the stale DTH issue : FAQ: My lock/device does not pair or appears to pair but it won't show up in the mobile app or IDE, remove all device handlers (or republish ALL device handlers one by one), then try to reset, exclude and pair it again within 5ft of the hub.
If it works then it was a stale DTH, now install the custom DTH and either switch the DTH or pair it again.
Another way to check if you’re running into the stale DTH issue, open the IDE -> My hubs -> Click on List Events, there you’ll see it pair successfully in the list of events. If you don’t see a device being paired after the pairing starts (you’ll have to refresh the page), then it’s a bad sensor.
If that still doesn’t work then you may have a bad batch of sensors. It happens sometimes, a few folks have reported it and usually RMA’ing it and getting a replacement solves the issue.