This error usually occurs when there have been too many failed connection attempts with a wrong email and/or password. When this happens, your IP is temporarily banned for 24 hours.
First, verify your email and password by logging in to your Genymotion account at https://www-v1.genymotion.com/account/login/ . If you can log in, just wait for 24 hours and try again with Genymotion Desktop.
If you can't log in, reset your password at https://www-v1.genymotion.com/account/password-reset/ and test it at https://www-v1.genymotion.com/account/login/. Then, wait for 24 hours and try logging in with Genymotion Desktop again.