Are you on a C-7 model Hubitat? (If you’re not sure and you bought it recently, the answer is probably “yes.” If you got prompted to enter the S2 DSK during pairing, the answer is definitely “yes.” But you can check in Settings > Hub Details or the bottom of the hub to be sure.)
If so, one thing that might help is shutting down the hub (from Settings), removing power after it shuts down (red LED on the front), then waiting about 30 seconds before plugging it back in. This will force the Z-Wave radio to restart and is one trick some users have had to do with stubborn devices, which can sometimes be the result of the radio getting hosed in a way that only this can help with (until Silicon Labs or whoever figures out what might be going on with the SDK Hubitat is using).
Additionally, despite the fact that you tried a reset, you might want to try an exclusion before inclusion just to be extra-sure. Z-Wave devices won’t pair if they already think they’re included, and a reset should also take care of that, but this can’t hurt. It is also good to try after any failed inclusion attempt.
Beyond that, the problems you are describing are odd, but it’s hard to say what the cause is. Do you have a strong Z-Wave mesh (with multiple other repeating devices)? Is the hub far away (repeaters should help with this and if the device can’t pair in place it probably won’t work in place either, but it may be helpful for troubleshooting)?
Finally, if you haven’t updated to Hubitat firmware 2.2.4 and are on a C-7, I’d try that, as there are multiple improvements over 2.2.3 for Z-Wave. (On a C-5 and earlier hub, nothing should have changed there.)