If the email address that was entered for login, is not an agent/contact in the account, then this error would be displayed. You could sign up for a new account, using the Sign Up option on the Portal, or ask to be added as an Agent from under Admin >Team > Agents in your account. Once this is done, you could log in to your Freshdesk Account.

If you continue to face issues with login, reach out to Freshdesk support through support@freshdesk.com to know the Agents on your Freshdesk account and we would assist you in getting over this instance.