Cannot SSH to ec2 instances

I'm posting because I can no long ssh to my ec2 instances. I've tried the steps found here https://aws.amazon.com/premiumsupport/knowledge-center/ec2-linux-resolve-ssh-connection-errors/ for restarting ssh. I've tried starting a new instance and ssh'ing into that, and that likewise times out. Based on an answer to this stackoverflow post: https://stackoverflow.com/a/55234006/848485, I'm posting here on the chance that my account has been "isolated". If anyone has anything else for me to try I'm happy to give it a go.