So I’ve yet to get downtime for this client to actually fix any type of configuration already done.
The LAN coming from the FE to the FG is 192.168.200.0, which they actually already have an internal lan with that schema (Handled by Extreme Gateway) is this why it’s breaking the network? It’s the only thing I can think of that would cause any type of issue.
It’s acting as a WAN extension and being put into SDWAN
If FGT already has another network in 192.168.200.x range and if you're trying to bring up another Network (FEX network) then yes it may create IP Network duplication situation. You can download FGT config backup and then try changing the existing FGT network to a new subnet if possible or simply change the default DHCP server range (192.168.200.x) range on the FEX to a new DHCP IP range via console access and then check if this solves the situation:
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