FortiGate FortiSwitch (FortiLink): LAN works but no internet via MPLS SD-WAN

Hello,

This is my current topology:

FortiGate → FortiSwitch (FortiLink) with the following VLANs:

• Data

• Voice

The FortiGate is also configured with SD-WAN using two MPLS interfaces.

The issue I'm seeing is the following:

When I connect a notebook to a port on the FortiSwitch, I can access all LAN devices without any problem. However, when I try to access the internet, for example by doing a ping, the traffic does not go beyond the Data VLAN gateway IP.

Important detail:
Both LAN and internet traffic should exit through the same MPLS path.

To validate the issue, I reverted the MPLS interfaces back to the Huawei device, and in that scenario the customer has both LAN and internet connectivity working correctly.

The configuration on the FortiGate is fairly straightforward, mainly BGP with SD-WAN, nothing unusual.

Has anyone seen a similar behavior or have any ideas on what could be causing this?

Thanks in advance.

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