You can't use special characters for the password. Solusvm client area supports alphanumeric passwords only. You can't use any special characters password(including !) from client panel. If you wish to set a highly secured password for you VPS you can follow the below steps.
1. Set a simple password (something like "changeme") via SolusVM panel.
2. Login to the server using SSH
ssh server IP
User: root
Password: changeme
3. Run the following command
password
It will prompt you to enter password
Now you can use the new password.
