Can't connect AirLink LX40 to Fortigate VPN (IPSEC)

I’ve taken over a job to get these routers to connect to the VPN running on out Fortigate 201E.

There are already routers connected to the VPN and i found these and setup the new routers with the same VPN information.

Everything is identical except ip ranges and stuff that needs to be different.

In the fortigate i’ve created an IPsec tunnel specifically for this device, it’s identical to the other tunnels except name and ip.

The only logs i can find that are related to this is on the router itself saying:

err ALEOS_VPN_SwanMgr: establishing CHILD_SA ‘tunnel1’ failed

What do i do here?