This seems to be a new issue since upgrading the firmware to version 22.214.171.124.
We are now getting what I call "Half-baked" devices upon discovery.
In the newer looking firmware Discovery page, there is a new button "Start Zigbee pairing" in the lower left, which used to be on the right as a button IIRC. I push that, our device debug says it gets onto the PAN-ID, on the hubitat a new line shows up below the "Start Zigbee pairing" button, and very quickly comes up with a "Found Devices:" line, and soon, below it is a box with
Found Zigbee Device with id F4CE3697D1494815
... and it progresses no further until the 60s timer expires.
Watching our own device's debug log, the Zigbee chip has connected, and, a sniffer evidences the traffic to and from the hubitat to our device.
Once in this mode, these half-baked devices never end up showing up in "Devices", yet the Zigbee chips between the hubitat and our device are talking on the same PAN-ID as evidenced in the sniffer.
Once the device is half-baked, I must factory reset our own device. If it is not factory reset, as soon as it boots, it finds the hubitat coordinator and thinks it is connected. The hubitat, however, has no "Device" in it's list, so, we can never get it to talk to our device.
Previous hubitat firmware versions would continue to do their "Initializing..." in the background, and sometimes even after 3 minutes, would eventually find our device, but this version seems to stop.