The "Server refused our key" error is most commonly seen when the SSH command is malformed.
Check your SSH command against your "Servers" page, which contains the correct path to H into your servers. To access your "Servers" page:
1. Sign in to Acquia Cloud.
2. Select your application, then the relevant environment.
3. In the menu to the left, click "Servers."
Read more about accessing your "Servers" page
See also:
SSH and RSA key warning: Remote host identification has changed