Putty, ssh and key-based authentication

Folks - I'm really looking to schedule scripted scp backups of configs.

To this end, I've generated a private key using puttygen, and loaded the public key on a 200D

e.g.

set ssh-public-key1 "ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAo3kJzIWxYYjCeLeWupefDBdMx+GRPZVUNaD/5ZBcAHGnnmHc2msudNb4Vxa86uMUvApWhjaMwp8lnnG+Ig90FV3zt3wx2siqKlyTZDIlDDr3NIVQaxBjyV0HwnAPcMUbm23mxV3g36EAkGc3BXONUBx3PxxCAPCEh3FqLHJda/o1gfGHnPyuO9T+3KzxJqPsl42ldQLkDb8Cn8klrWJyuCzxh1rDYVYOd/XxtLDNQzsDC9oHajA9f2bK2lwEtewa134Dj2T1iQohJIiC9O7xnEakDErTFtKaR1xZrGx87RAIRWTrgSo/MPoUiZHDp5CfERyp1CB2tv5hW06OFymVrQ=="

Point to the private key in putty, set the user, but only receive a cryptic 'server refused our key' back from putty.

Is there any way to log on the 200D side why the key is not being accepted? Or any other approach I should try?

Many thanks for any insight you might offer.

Cheers - Pete