VLAN not showing up in DHCP
I made a mistake with a VLAN configuration and when I modified it to what it was meant to be (There were no warnings about the DHCP server) I now cannot see my VLAN under the DHCP service, I am now getting alerts all the time such as
Invalid DHCP pool 192.168.120.101 - 192.168.120.250 for VLAN20 subnet 192.168.120.252/32 detected. Please correct the settings in Services, DHCP Server
I have tried taking the working configuration from the Primary PFSense and restoring it to the second one (which is the one having this issue) and had no luck.
What's your subnet range in vlan20? Maybe it's not covering the address pool assigned in DHCP?
The problem is right there :) You seem to have accidentally configured the interface with a /32 subnet mask. DHCP can not be configured when there's no address space to use ;) As you wrote about primary and secondary: did you check BOTH nodes, that both have e.g. a /24 subnet selection in their VLAN20 interface config?