Cloning keys isn't possible, when crafted I get normal key!
However this feature works with the older version SerialKey v0.4
but not with the latest 1.0.1

Are you on Sponge or on Bukkit ?

Bukkit

Which version, what are your permissions, how did you come to that error, is there something in your console, ... ? Please add more details ^^

I tried the latest of
Paper, Bukkit, Spigot
[1.13.2]
All same issue
the cloned keys comes normal keys
but with the older version SerialKey v0.4 cloning works fine

No console errors
I use LuckPerms [Tested With and Without it] and I'm OP
Also I tested with no other plugins in a clean server and as operator
Same issue

Thank you. I'm going to check this tomorrow.

Done (the link will be active when the file will be approved by the Bukkit staff).