AWS CloudFormation模板创建EC2实例后无法连接求助

我使用以下AWS CloudFormation模板成功创建了EC2实例，但无法通过Instance Connect或Putty的SSH方式连接该实例。已按建议为子网关联Internet Gateway，但问题仍未解决。

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Metadata": {
    "AWS::CloudFormation::Designer": {...}
  },
  "Resources": {
    "vpc1": {...},
    "subnet1": {...},
    "secGrp1": {...},
    "ec2": {...},
    "instanceProfile1": {...},
    "ig1": {...},
    "gateway1": {...},
    "role1": {...}
  }
}

相关错误信息：

• 堆栈事件日志：截图显示堆栈资源创建完成的事件记录
• Putty连接超时错误：提示「Network error: Connection timed out」
• Instance Connect错误：提示「There was a problem connecting to your instance」，下方显示「Failed to connect to your instance. Please try again.」

更新1：
我在CloudFormation中添加了Network ACL配置，错误发生变化但仍无法连接：

"netAcl1": {
  "Type": "AWS::EC2::NetworkAcl",...
},
"MyNetworkAclInboundRule": {...},
"MyNetworkAclOutboundRule": {...}

新错误提示：「Failed to connect to your instance. Error establishing SSH connection: Connection refused」

内容的提问来源于stack exchange，提问作者Devashish Priyadarshi