It usually means that the PuTTY settings are not set correctly for logging in. You should use these settings:
-- Host Name: enter IP of your server
-- Port: 22 (leave as default)
-- Connection Type: SSH (leave as default)
Then Click "Open" to start the SSH session. If this is your first time connecting to the server from this computer, you will see "PuTTY Security Alert" table. Accept the connection by clicking "Yes". Once the SSH Connection is open, you should see a terminal prompt asking for your username. Next, enter your password. Please note that you will NOT see your cursor moving, or any characters typed, when typing your password. This is a standard PuTTY security feature. After you typed it in hit enter.
Make sure you have a correct password. Also one of the other possible reasons could be that your device is blocking the connection or the port you are using.