Permission denied (publickey) on ubuntu 16.04

$ ssh mykey.pem ubuntu@10.128.2.7 -v OpenSSH_7.3p1, OpenSSL 1.0.2j 26 Sep 2016 debug1: Reading configuration data /c/Users/works/.ssh/config debug1: Reading configuration data /etc/ssh/ssh_config debug1: Connecting to 10.128.2.7 [10.128.2.7] port 22. debug1: Connection established. debug1: key_load_public: No such file or directory debug1: identity file /c/Users/works/Documents/interface setup/ifx_key.pem type -1 debug1: key_load_public: No such file or directory debug1: identity file /c/Users/works/Documents/interface setup/ifx_key.pem-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_7.3 debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8 debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8 pat OpenSSH_6.6.1* compat 0x04000000 debug1: Authenticating to 10.128.2.7:22 as 'ubuntu' debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: algorithm: curve25519-sha256@libssh.org debug1: kex: host key algorithm: ecdsa-sha2-nistp256 debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: compression: none debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: compression: none debug1: expecting SSH2_MSG_KEX_ECDH_REPLY debug1: Server host key: ecdsa-sha2-nistp256 SHA256:R+d2ELtCJyoeyHMfivCsGKk98GOIfxxsTEPAFmKkSOI debug1: Host '10.128.2.7' is known and matches the ECDSA host key. debug1: Found key in /c/Users/works/.ssh/known_hosts:1 debug1: rekey after 134217728 blocks debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: rekey after 134217728 blocks debug1: SSH2_MSG_NEWKEYS received debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey debug1: Next authentication method: publickey debug1: Trying private key: /c/Users/works/Documents/interface setup/ifx_key.pem debug1: Authentications that can continue: publickey debug1: No more authentication methods to try. Permission denied (publickey). I used to be able to ssh into this machine until yesterday. Is there a way to login into it?