Unable to upload: "Permission denied (publickey)"

[Adam Dinwoodie]

I'm currently unable to upload packages I maintain: attempting to
connect to cygwin@cygwin.com over SSH or SFTP is failing.  I'm
reasonably confident I haven't done anything locally to change my key;
has something happened server-side to cause problems?

    Wed 22 Nov 14:54 $ sftp -i ~/.ssh/cygwin_rsa cygwin@cygwin.com
    cygwin@cygwin.com: Permission denied (publickey).
    Connection closed

Happy to provide more detailed diagnostics if they'd be useful, but I'm
guessing the problem is either going to be resolved by fixing something
server-side or just re-uploading my SSH public key.

Cheers,

Adam