Assuming that nothing has been changed on the ESXi host, it's got to be some configuration issue on pfSense (or a physical switch!?).
Are both - vmnic0, and vmnic1 - connected to physical uplink ports on which VLAN12 is configured/allowed?
Are you able to reach/ping the default gateway for VLAN12 from other systems on the network (i.e. is routing configured properly)?
André