unable to create plugins due to vnet error

On a clean TrueNAS CORE 12.0 server, I've started from scratch and tried to create a syncthing jail. I issued iocage clean -a to completely remove all previous jail creation attempts.
When I first attempt to create a jail, I'm prompted for which pool to select.
I select as required and I'm presented with the list of offical plugins
I opt to create a syncthing jail
I leave the plugin name as default
I set the jail name to syncthing_1
I uncheck NAT
I select the IPv4 interface
I specify my IP address
I select the IPv4 netmask
I click Save
I then get an error: syncthing_1 had a failure Exception: RuntimeError Message: Stopped syncthing_1 due to VNET failure Partial plugin destroyed
In a past forum post, I read that specifying the IPv4 interface causes this issue so I try again without the IPv4 interface select.
I then get an error: Jail: syncthing_1 has a missing configuration, please check that the dataset is mounted.
I've confirmed my pool is mounted (otherwise my SMB shared will not work).
This happens with any plugin I try to create.
Screenshots and debug are attached.