I did the factory reset on the switch hold config for 20 seconds till the indicator light turns red then push 3 more times to set it back to what look like factory reset
Since it's a Red Gen 2 series (which is a bit dated) and this is your first device, I'm going to guess that the switch has been paired with another system previously. With Z-wave devices, you need to exclude them first before they can be added to a new hub. Factory resetting alone won't do that.
Do a general exclusion in Hubitat and exclude the dimmer. Then try adding it again.