When mounting an S3 bucket on an ubuntu EC2 instance with S3FS, SSH connection is not possible

Question

As stated above, I mounted an S3 bucket with S3FS on an ubuntu instance that I was able to SSH to, and when I restarted the instance, SSH connection to the instance was no longer possible.

ssh command

ssh -i "pem filename" ubuntu@"ec2-domain-name"

Error message

ssh: connect to host "ec2-domain name" port 22: Connection refused

This event did not occur until 2/28/2022, but started to occur on 3/1/2022. Please let me know if you know the solution or if you have encountered the same issue.