fortiswitch initial setup with management vlan via trunk

We have many cisco 2960s switches that we want to replace with fortiswitch 448d-poe, but are having trouble setting up the management interface.  We want port 48 to trunk all our vlans from our core switch to the fortiswitch.  We want the management interface to internally connect to the trunk (not use dedicated physical port) and use vlan37 and ip 172.25.37.31/24  Below is the config we have so far, but we cannot ping 172.25.37.31 from our core switch.  What are we missing?  Thanks in advance for your help.

idf3 # show switch trunk config switch trunk     edit "trunk1"             set members "port48"     next end idf3 # show system interface config system interface     edit "mgmt"         set mode dhcp         set allowaccess ping https ssh         set type physical         set secondary-IP enable         set snmp-index 55         set defaultgw enable             config secondaryip                 edit 1                     set ip 192.168.1.99 255.255.255.0                     set allowaccess ping https ssh                 next             end     next     edit "internal"         set type physical         set snmp-index 54     next     edit "vlan37"         set ip 172.25.37.31 255.255.255.0         set allowaccess ping https ssh         set snmp-index 56         set vlanid 37         set interface "internal"     next end idf3 #