Not able to ping from Fortigate to Switch

Hi All,

I am running through this problem since yesterday. Here goes my setup:-
I have got a fortigate 50E and it has got a LAN interface 192.168.49.1/24 and there's a core switch (Cisco) with 192.168.49.2. VLANs configured on Switch are 49 and 50. I want to introduce a new VLAN and when I try to create a subinterface (VLAN 3 and IP : 192.168.51.1/24)on LAN interface in FortiGate and giving VLAN interface IP on Core Switch as 192.168.51.2 I'm unable to ping from core to Fortigate (newly created subinterface 192.168.51.1) and vice versa. Can somebody help with this? I have created a DHCP scope on Fortigate itself and for other VLANs it's on Core Switch. I'm I missing something? have tagged the new VLAN on the interface which is connected to the Firewall interface. Also, there is a default route from Core to Fortigate (0.0.0.0 0.0.0.0 192.168.49.1).

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Please help!