Instance reachability check failed Error in AWS ec2

Greetings everyone!

We are currently experiencing SMART 6 server error which we are not familiar with. The server access through the Putty application always says “Network Error. Connection”. Upon checking with the AWS server, the instance state is running. However, there is an error of “Instance reachability check failed”.

We have already tried to reboot the instance using the AWS but still, we can’t up the server. Can anyone help us with this issue?

Thank you! Regards