无法通过Jumpbox连接私有EC2实例 技术求助

• 可正常连接Jumpbox实例，但从Jumpbox通过SSH连接私有EC2时失败
• 推测问题与密钥对相关，但我的AWS账号仅存在一对密钥对，此前从未出现该问题，目前已卡壳数日
• SSH连接私有实例时会提示两次ECDSA密钥指纹，怀疑这是问题诱因，恳请有相关经验的人士提供技术指导

Jumpbox实例及安全组CloudFormation配置 #

JUMPBOXSecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties: 
  GroupDescription: 'JUMPBOX Security Group'
  GroupName: JUMPBOXSG
  SecurityGroupIngress: 
   - CidrIp: 0.0.0.0/0
     Description: 'SSH from my IP address'
     FromPort: 22
     ToPort: 22
     IpProtocol: tcp 
  VpcId: !Ref Myvpc
  Tags:
     - Key: Name
       Value: JUMPBOXSecurityGroup 

JUMPBOXEC2Instance:
Type: AWS::EC2::Instance
Properties:
ImageId: ami-08e4e35cccc6189f4
InstanceType: t2.micro
NetworkInterfaces:
- AssociatePublicIpAddress: "true"
DeviceIndex: "0"  ### dodeluva public ip adressa na prviot interface
SubnetId: !Ref MyPublicSubnet
GroupSet:
- !Ref JUMPBOXSecurityGroup
KeyName: Key
Tags:
- Key: Name
Value: JUMPBOXEC2Instance

公有EC2实例及安全组CloudFormation配置 #

MyPublicEC2InstanceSG:
Type: AWS::EC2::SecurityGroup
Properties: 
  GroupDescription: 'Public EC2 Security Group'
  SecurityGroupIngress: 
   - CidrIp: 0.0.0.0/0
     Description: 'http from everuwhere'
     FromPort: 80
     ToPort: 80
     IpProtocol: tcp
   - SourceSecurityGroupId: !Ref JUMPBOXSecurityGroup
     Description: 'ssh from Jumpbox'
     FromPort: 22
     ToPort: 22
     IpProtocol: tcp     
  VpcId: !Ref Myvpc
  Tags:
     - Key: Name
       Value: MyPublicEC2InstanceSG

MyPublicEC2Instance:

Type: AWS::EC2::Instance
Properties:
ImageId: ami-0b5eea76982371e91
InstanceType: t2.micro
NetworkInterfaces:
- AssociatePublicIpAddress: "true"
DeviceIndex: "0"  ### dodeluva public ip adressa na prviot network interface
SubnetId: !Ref MyPublicSubnet
GroupSet:
- !Ref MyPublicEC2InstanceSG
KeyName: Key
Tags:
- Key: Name
Value: MyPublicEC2Instance

内容的提问来源于stack exchange，提问作者UchihaMalo