GCE – Unable to SSH to GCE: ‘Permission Denied (publickey)’

I created a VM via Bitnami in Google Compute Engine. Previously, I was able to ssh via the Bitnami web interface. I tried to ssh via terminal on my Mac but kept getting the Permission denied (publickey) error. I then deleted all keys on the server and my Mac and downloaded the pem file form bitnami and used -i option to connect but still the problem persists.

ssh -i bitnami-gce.pem xxx@1xx.1xx.5x.1xx -v

Complete debug info:

OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 20: Applying options for *
debug1: Connecting to 1xx.1xx.5x.1xx [1xx.1xx.5x.1xx] port 22.
debug1: Connection established.
debug1: identity file bitnami-gce.pem type -1
debug1: identity file bitnami-gce.pem-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Debian-4~bpo70+1
debug1: match: OpenSSH_6.6.1p1 Debian-4~bpo70+1 pat OpenSSH*
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5-etm@openssh.com none
debug1: kex: client->server aes128-ctr hmac-md5-etm@openssh.com none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Server host key: RSA <RSA KEY>
debug1: Host '1xx.1xx.5x.1xx' is known and matches the RSA host key.
debug1: Found key in /Users/xxx/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: bitnami-gce.pem
debug1: read PEM private key done: type RSA
debug1: Authentications that can continue: publickey
debug1: No more authentication methods to try.
Permission denied (publickey).

I am unable to ssh to the host. So can't send any keys to server now. How to resolve this?

Edit: I tried to ssh via Google web console and I could do it. Can anyone tell me the exact steps to ssh from anywhere? I prefer the simple username and password way, how to configure it that way?