atlassian pipeline Host key verification failed

Question

I would like some help, I'm trying to automate the upload of a .jar file using atlassian pipelines. Everthing compiles and runs ok until it's time to upload the file. Where I get

INFO: Configuring ssh with default ssh key.
INFO: Adding known hosts...
INFO: Appending to ssh config file private key path
INFO: Applied file permissions to ssh directory.
Host key verification failed.
scp: Connection closed
✖ Deployment failed.

I have a .pem file thats what I usually use to scp files to the remote server, opening it as a .txt for the private key and using ssh-keygen -f private.pem -y > public.pub command to get the public key I added everything in the admin/pipelines/ssh-keys URL of my repository cliking the 'Use my own keys' option. I copied and pasted literally everything that was on the files.

I also have some repository variables than I'm using on my .YML file, the file looks like this:

image: openjdk:8

pipelines:
  default:
    - step:
        name: Compile
        script: 
          - javac -cp "./libs/*" ./src/com/company/myprogram/**/*.java
          - jar cvfm ./MyApp.jar ./Manifest.txt ./src/com/company/myprogram/main/MyApp.class
          - ls -R $BITBUCKET_CLONE_DIR 
        artifacts:
          - MyApp.jar
    - step:
        name: Deploy to QA server
        script:
          - ls -R $BITBUCKET_CLONE_DIR
          - pipe: atlassian/scp-deploy:1.4.1
            variables:
              USER: ${USER}
              SERVER: ${HOST}
              REMOTE_PATH: '/home/myuser/'
              LOCAL_PATH: './MyApp.jar'  

I have been reading about it for some time and modifying everything to see if I get it to work, but no luck. Help please!