Using Lost Cities 1.0.0 and the /locate Mansion command returns "Unable to locate any Mansion feature". Config is rarecities and confirmed Mansion Structure setting set true. Attaching screenshot with relevant seed.

Seed - 5467926135997939143
x - 1608
z - 6920

# Generate mansions
B:generateMansions=true

You need to use 'LostMansion' instead of 'Mansion'. Also only on 1.12

Did you modify the command structure? The Vanilla command is "/locate Mansion" as documented on the Minecraft Wiki - https://minecraft.gamepedia.com/Commands/locate

I did not modify it. But I was not able to add mansions to Lost City worlds. So I had to replicate mensions to my own structure which need to have another name. That's why you need to use LostMansion. Because technically they are not the vanilla mansions (but completely look and behave the same) but my own

Gotcha, thanks for the explanation.