Server refused your key error prevents SSH from connecting to the EC2 instance

About AWS SSH Connections

·Current status
We have signed an AWS EC2 contract.The instance started successfully.
Allows SSH on security inbound and specifies its own IP address.
Created a key pair.Downloaded the pem file.

·What you want to do
I want to make SSH and SFTP connections to AWS.

·Situation and questions
Loaded the pem created in AWS and created a private key.
I tried to make an SSH connection with putty while browsing AWS Help.
After entering the username, the
Server refused your key message appears. SSH connection failed as indicated by Putty.

To create a private key, follow these steps: https://docs.aws.amazon.com/ja_jp/AWSEC2/latest/UserGuide/putty.html
See
I set up the ppk file when connecting on the putty side, but as mentioned above
SSH connection is not successful when prompted.

The hostname and port number were not invalid when the SSH connection was attempted.
Which part should I check?