File system error occurs when root volume of EC2 instance is reduced and reconnected.

<Working instructions in this article > formatting xfs with ext4 may indicate that the file system is corrupted.

At the beginning of the referenced article

Depending on your Linux and partition configuration, the method may vary.
This article provides an example procedure for the following environments:

• Using LVM
• The boot loader is GRUB2 (using Stage 1.5)
• The operating system is Linux (RedHatEnterpriseLinux 7.5)
• EC2 for work is t2 instance

It says.I understand that there is an error in the grub, but does the condition match that the boot loader is GRUB2 (using Stage 1.5)? I don't know because there is no information about the environment in the questionnaire, but if it doesn't match, I think we need to do something else.

The status check will fail 1/2 no matter what.

The status check may be considered a black box, but it is explained to some extent by the instance status check.There are two types of status checks:

• Checking System Status
  Hardware health checks primarily responsible for AWS.
• Check Instance Status
  Check if the network interface responds to ARP.Because the OS cannot respond to ARP without initializing the network interface and giving it an IP address, it acts as a check to see if the OS is able to initialize.

Strictly speaking, you need to look at the instance metrics, but I think it's 1/2 because the instance status check almost certainly failed from the background of the question.
The cause is clear, and the OS has not been able to boot to the point where it initializes the network interface.
As long as the network interface has not been initialized, it is natural that it cannot ssh.