EC2 SSH port 22 connection refused even though previously worked

I have an EC2 instance which i've got a couple of sites hosted on and it's previously been workin really nice.

Today I try to SSH into it and it just refusing connections on port 22 even though the security group has it open and the security group is set to the instance.

Anyone help me out as to why this could be the case?

I just get this line each time - ssh: connect to host 54.247.99.86 port 22: Connection refused