Troubleshooting SFTP Connection Errors: “HostKey Has Been Changed” & “Access Denied”

Overview

This article outlines how to troubleshoot two common SFTP issues encountered when configuring third-party connections in Amperity:

  1. HostKey has been changed errors during connection tests

  2. Access denied errors when browsing folders on an SFTP server

These issues typically arise due to misconfigured credentials or incorrect assumptions about SFTP account permissions.

1. “HostKey Has Been Changed”

This error usually indicates that an incorrect Host Public Key was entered into the Amperity SFTP credential.

  • The Host Public Key field should almost always be blank.

  • Customers sometimes paste their SSH public key into this field by mistake.

  • The field is only used in rare cases where a customer requires pinning to a specific server HostKey.

    Fixing the HostKey Error

  • Go to the SFTP credential in Sources → Credentials.

  • Open the SFTP credential configuration.

  • Locate the Host Public Key field.

  • Remove any value from this field (leave it blank).

  • Save the credential.

  • Re-run the Connection Test from the courier or credential.

Once the incorrect Host Public Key is removed, the connection should succeed.

2. “Access Denied” When Browsing

  • All logins for an Amperity SFTP account have access to any paths below the account’s root folder.

  Fixing the Access Denied Issue

  • User must create a separate SFTP account dedicated to that third party under the root folder. 
    SFTP User name convention :  <tenant-id>_<thirdpartyname>
     

This error most likely indicates a permissions issue:

For Amperity SFTP – ensure that the credential is updated.

For third-party SFTP – verify folder permissions and access structure on the third-party side.

  • Note: If a customer needs an additional SFTP login for a third party, they must contact Amperity Support to provision a new SFTP folder and associated credentials.