I had the same issue, so I first SSH into the server to confirm that I able to log in to the server by using the command:
ssh -i /Users/Desktop/mypemfile.pem [email protected]
Then in New Terminal
I copied a small file to the server by using SCP, to make sure I am able to make a connection:
scp -i /Users/Desktop/mypemfile.pem /Users/Desktop/test.file [email protected]:/home/user/test/
Then In the same new terminal, I tried running rsync:
rsync -avz -e "ssh -i /Users/Desktop/mypemfile.pem" /Users/Desktop/backup/image.img.gz [email protected]: