Connecting to EC2 Instance via Terminal on Mac - macos

Question

I am completely new to coding and am doing a startup course on coursera: https://class.coursera.org/startup-001/lecture/87
I'm getting a Permission Denied (publickey) when trying to connect to an EC2 Ubuntu Instance I created on AWS
Set up AWS Istance
Set Security to default and added port 22 and launched
Course tells me to then type:
chmod 400 trevor-learning.pem
ssh -i trevor-learning.pem \ ec2-user#ec2-XX-XXX-XX-XX.us-west-2.compute.amazonaws.com
This then gives me this error: Permission denied (publickey).
I've looked at other questions asked and tried switching the ubuntu# to ec2-user and some other things but I still can't connect.
I also tried:
trevor-larsons-macbook-pro:downloads trev$ chmod 600 trevor-learning.pem
trevor-larsons-macbook-pro:downloads trev$ ssh -v -i trevor-learning ubuntu#ec2-XX-XXX-XX- XX.us-west-2.compute.amazonaws.com
which gave me:
OpenSSH_5.9p1, OpenSSL 0.9.8x 10 May 2012
Warning: Identity file trevor-learning not accessible: No such file or directory.
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 20: Applying options for *
debug1: Connecting to ec2-XX-XXX-XX-XX.us-west-2.compute.amazonaws.com [XX.XXX.XX.XX] port 22.
debug1: Connection established.
debug1: identity file /Users/trev/.ssh/id_rsa type -1
debug1: identity file /Users/trev/.ssh/id_rsa-cert type -1
debug1: identity file /Users/trev/.ssh/id_dsa type -1
debug1: identity file /Users/trev/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 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 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
debug1: Host 'ec2-XX-XXX-XX-XX.us-west-2.compute.amazonaws.com' is known and matches the RSA host key.
debug1: Found key in /Users/trev/.ssh/known_hosts:2
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: /Users/trev/.ssh/id_rsa
debug1: Trying private key: /Users/trev/.ssh/id_dsa
debug1: No more authentication methods to try.
Permission denied (publickey).
At a loss here and have NO idea what I am doing please help!
Also, not sure if this has anythign to do with it, when I download the instance certificate (shows up bottom left of chrome browser, it opens up my keychain access and says" an error has occured. unable to import an item. the contents of this item cannot be retrieved."

Answer 1

Try the following steps in your terminal:
ssh-keygen -R 12.345.678.999 // This Reset your publickey
Then try to access with your Key Pair Name and Public DNS of EC2:
ssh -i KeyPairName.pem ubuntu#ec2-xx-xxx-xxx-xxx.eu-west-1.compute.amazonaws.com