Hello, I am new here.

I am experimenting with a full node, and setup a new node on ubuntu - Core 0.16.0.
I'm running my bitcoind in test-net

I am having an issue running signmessage [key] [message].  Whenever I try to sign a message with my pub key, it shows this error

Steps:

1. bitcoin-cli getnewaddress
--> It produced an address: 2N2yv1XcYfNXR54J7ZJvBxY6ZnmZFbz89tm

2. bitcoin-cli signmessage "2N2yv1XcYfNXR54J7ZJvBxY6ZnmZFbz89tm" "Hello there"

--> Get following error
error code: -3
error message:
Address does not refer to key


This is pretty vanilla functionality - why is this happening and how to address?

Thank you in advance.