With these settings I tried to pair it with the very first Zigbee device, a SmartThings Button, but the pairing process wouldn't find the button. I started with the button a couple of rooms away from the hub, but the button is now sitting right in front of the hub and it still cannot find it. I've tried all pairing modes available but it won't find it using any of the modes.
I tried adding the button to another hub (a C7 running 2.3.8.140) and it added just fine.
I pulled out an IKEA signal repeater and tried adding that to the C8 Pro. Same result with this one; the hub just won't find it.
I've restarted the Zigbee radio, I've shut down and unplugged the hub, increased the power level to the maximum and even swapped the antennas with each other just in case, but nothing has made a difference.
When I do a Zigbee channel search I get zeros for all channels:
I have three Zigbee channels in use and other HE hubs identify all these channels, but this hub doesn't. Makes me think something with the Zigbee radio isn't working properly.
I swapped the USB power adapter and cable that came with the hub with other ones I had and all of a sudden I'm getting results from my Zigbee channel scan:
I played around with different combinations of USB cables and power adapters, but now Zigbee has stopped working again, even with cable and adapter combinations that worked before. It still thinks Zigbee is working though:
No joy with 21, 22, 24 or 26. Radio reboot after each channel change and a shutdown and power removal for good measure but all to no avail. Changed back to channel 20 again...
2.4 GHz WiFi channels in use are 1 and 6 btw, so I shouldn't have any issues with interference from WiFi.
At some point I noticed the LED light on the hub flashing red-green-red-green a few times and then settled on solid green again. I wasn't doing anything on the hub at that point.
Do you see anything in the live logs when you try to pair a Zigbee device?
Anything in Settings->Zigbee Details->Logs ? (Keep this page open on browser tab).
When pairing, have you ever seen a message ‘Zigbee device found, initialising….’ but the process never finishes successfully , or nothing happens at all?
Seeing the hub cannot find anything when doing the Zigbee channel scan, it leads me to believe that there's something wrong with the Zigbee radio or the connection between the radio and the antenna.
Edit: If there is a break in the connection between the radio and the antenna, that could explain why the Zigbee channel search returned results a few times. That happened when I was testing different power cables and adapters, so I was physically moving the hub around between those tests. Moving the hub one time there might have been enough to get a connection across the break in the connection between the antenna and the radio but then moving it subsequent times the connection was again severed. That could also explain why the hub thinks that Zigbee is online. The radio is working and is online, it's just that it cannot hear anything with no connection to the antenna
This looks like a Zigbee radio malfunction.
I have made experiments with my C-8 working with the external antenna detached, it works just fine with Zigbee device that is put a meter away.
So... I received a replacement hub... And it exhibits the same issue - unable to detect any Zigbee devices to pair with and not detecting any of the other Zigbee channels in use when doing a Zigbee channel scan. Surely it cannot be two hubs having the same issue.
I removed the hub from its intended location and put it in the office where I can more readily play with it. And just like that, the hub works. I could reliably reproduce the issue by putting the hub back on top of the comms cabinet where all my other hubs (HE and others) live. Ok, so I thought it must be an interference issue from the other radios in the vicinity, so I shut down and removed the power from the other hubs, one by one, until everything in the comms cabinet was shut down, except for the new HE hub, and it still wouldn't work.
If I separate the hub from the metal of the comms cabinet by hanging it dangling off the side of the cabinet or by putting it on a box on top of the cabinet, Zigbee works. The only thing I can think of causing this would be if there is some sort of protection mechanism in the Zigbee radio that detects that some of the signal bounces back (from the metal cabinet) to the antenna very quickly and strongly and then shuts down parts of the radio to protect itself. Unfortunately, this wasn't reflected in the Zigbee status on the hub as it still appeared to be "online".
TL;DR - Lesson learnt: not only shouldn't the hub be placed inside a metal cabinet, it may not even work when placed on top of one.
Wow that is super frustrating. You could consider putting the hub into the cabinet and get some extension cables for your antennas. This long thread has some good information
After months of frustration, on the day I had decided to give up and move back from a C8 Pro to a C7, out of curiosity, I came to this forum for a last check, and I'm very glad I did! Your message pointed my in the right direction.
What I have to add
Metal cases/cabinets aren't the only potential issue, my hub is inside a plastic enclosure and I was having nightmares with it.
After reading your message I have decided to change the position of the hub, and like you, I have left it hanging just outside the enclosure, very close to where it was before, but to my surprise it fixed the issue too!
Inside the enclosure it was very near other electronic devices and their power supplies, this seems to cause powerful interferences with the Zigbee signal.
After confirming it had fixed the issue, I have moved it back inside the plastic enclosure, but not so close to other electric/electronic devices. It has been working well so far.
My C7 never had any problems in the exact same place, which leads me to believe that the C8 and C8 Pro models are way more susceptible to interferences than the C7.
In case someone is curious, here is a more detailed report.
I have a strong mesh, currently 76 repeaters out of 82 total Zigbee devices, several are inside the same (big) plastic enclosure as the hub.
The problems with C8 Pro would vary and could come and go without any changes to the hub or the devices. These include:
Zigbee command delays
Ranging from milliseconds to more than 60 seconds
Commands failing to execute
This could affect anything from a single device, to, more commonly, almost all or all devices.
A mix of the previous problems
The mesh was very unreliable. It could work perfectly for weeks or even months and then, normally after a reboot nothing would work. Getting it to work again was a painful, frustrating and time consuming task.
I hope these details can help others who may face similar issues.
