I have this problem too. I am trying to proof the ownership of my address via signing the message. Steps to reproduce:
1) I download Bitcoin Core 0.16.0
2) Have started bitcoin-qt.exe
3) Generate new adress: 32iCzcXZefA9j84Q2A7EXPUwRwA6bykQij
4) When i tried to sign message with this adress
it shows an Error:
The entered address does not refer to a key. Please check the address and try again.
How i can sign message and proof my ownership of my address?
What I am doing wrong?