SSH from Mac gives error

It maybe seems to be not AWS problem but your mac environment problem.

is '/Userkeypair.pem' really your EC2 instance's identity file?
If so, Try specifying your identity file in your computer with an absolute path.

If you still get an error, write the command you just executed.

Make sure you are ssh in the same directory with the correct .pem file. Also change the permissions on the file so that only you (as the file owner) can read it. I ran into the same error when trying to ssh to my website about best stock research websites