Non root user unable to login with ssh key

I have had several droplets in the past and not had this problem before.

I have copied an existing ssh key to a new droplet (Fedora 31) and am able to login via ssh key without issue with root.

When I copy another key over for a non root user I am always prompted for the password, this however does work on an older droplet I have.

This is all through the sshd service:

If I start another instance of sshd in debug mode with …

/usr/sbin/sshd -d -p 2222

… and then connect with …

ssh -p 2222 <username>@<ip_addr>

… it works fine and I am not prompted for a password.

I have not altered /etc/ssh/sshd_config at all and cannot see any significant difference between the one on a FC27 droplet to the one on this new FC31 droplet.

I have checked the ~/.ssh permissions for the user and all is as it should be.

Has something change between FC27 and FC31? Am I missing a configuration directive?

Any suggestions would be greatly appreciated.