I'm very new to Hubitat and have a C8. I have a few (non-Zigbee) devices connected and all good with them. However I have tried to directly pair a Hue Dimmer Switch (V1) and also a Ikea Tradfri Plug using the Devices -> Add devices -> Find By Brand route and they will not pair. I have reset both the Hue & Tradfri items and nothing happens during the pairing cycle.
Is there any way I can check to see if the Zigbee element of my C8 is actually working?
Swap your antennas and give it another go.
Thanks for the suggestion. Assume you mean swap the two provided around? I just did that and still no success 
Grab the latest firmware 2.3.5.121... we've been busy making adjustments to Zigbee based on the post-release feedback.
If the hub is running the latest already, can you PM me the hub id? I'll check the engineering logs.
I am on 2.3.5.121 (upgraded today), problem persists before/after upgrade. I will send you the Hub ID.
same here, cannot pair Aurora zigbee plugs which are among the compatible devices with drivers. Hub is fairly useless at the moment TBH 
Did you manage to look at the logs @gopher.ny
Have you had any luck with your issue? I'm still having issues with my C8....
Hi @gopher.ny I sent you my hub-id a few days ago. Have you had chance to look at the engineering logs. I'm pretty-stuck here, with a new shiny paperweight (at least from a Zigbee perspective). Any advice appreciated.
Overall silence on this issue is not helping things at all. I can understand issues and taking time working through them but, silence for this long is making things worse from where I sit.
Indeed. I'm coming here from Home Assistant and unless things improve soon, it's looking like I will be returning my C8 and scurrying back to HA. Like you say the 'silence' is the most frustrating thing. I accept there will be issues along-the-way, but little/no communication doesn't boost the confidence.
Hubitat @support_team has been very busy w/multiple FW updates for the C8 and helping customers who are experiencing related issues. I'm sure they will be able to help soon.
@NotBernard65 @mpoole32 - Have either of you tried moving the devices close to the hub to see if that makes any difference during pairing attempts? Do you see any messages when attempting a pairing? Or just the timer counting down?
How about just doing a standard zigbee pairing (don't use the by brand/model method)
Just roll the firmware back to when you first received the hub. You should be able to pair devices then.
My issues go way beyond just a device not pairing.
Sengled bulbs are still an issue. Sensors that worked on C3 and C5 don't work.
All as I wrote before made worse by no communication.
The forum is full of posts made by those dealing with these issues.
Doing things like moving a device closer to the hub to see if it might possibly pair is shooting in the dark which is also what my wife experiences when she walks in a room and those sengled bulbs don't come on. It's a coin toss at this point if it's the bulb or the sensor that's misbehaving.
I've had the C8 now for a month and that for me under these circumstances is where my patience starts to run out.
Some success, mainly through resilience, not skill or technique. I never got my zigbee plugs to pair (despite them being on the compatible list), but have managed to pair a different brand now (which are NOT on the compatible list) using a generic driver. Didn't get a sonoff motion detector to work, or one from another brand (same as the plugs that worked!). Have today got some sonoff door sensors to work. Still feels very unstable and I'm not filled with confidence that any given device will work!
I'm not sure what version it actually shipped with (since I did an immediate upgrade on installation), however I did subseqently upgrade it again, so the issue I have has unfortunatly persisted over two versions.
Devices were in close proximity of the C8. No messages. just the countdown to zero.
Just pick the earliest one. I'm pretty confident you will be able to pair devices. then when the Hubitat team gets things worked out upgrade then.
What do you have?
Make sure to Reset the Zigbee Radio
FWIW I have had the opposite experience, device pairing and persistence on my Zigbee mesh has improved from early releases to current. Currently on .121 both Sengled bulbs and Hue motion (initially my hardest devices to keep connected) are both solid again.
But given the range of experiences we're seeing here (from zero issues/all working to significant/blocking problems), makes sense to try a range of things, including falling back to an earlier release to see if it helps. 
FWIW, problems w/Sengled bulbs (in my case color and bright 1500 lumen versions) actually began on the C7 well before the C8 release (after being perfect for me for >3 years). Others in the forum were starting to report issues on the C7 before the C8 as well. However, as of .121 on the C8 my Sengled are once again staying connected/solid, so the bulbs are pairing/working well on some meshes. Just not all, and finding the reason(s) why the differences has not been easy.
Two areas to look into:
Zigbee transmission power level: The C8 has an antenna and ships w/it set to power level 16. The C7 had the rough equivalent of power level 8. Some have improved results by lowering their C8 Zigbee power setting. Settings>Zigbee Details
Wi-Fi interference: Given the higher power of the C8 antenna, the 2.4ghz C8 Zigbee signal may be more likely experience interference w/2.4ghz Wi-Fi. See info below, worth checking/ruling out:
Download the Hubitat app
