RockMelt couldn't login

Dears,

Please I need your support, I installed Rockmelt and tried many times to login to Rockmelt facebook account
But in vain
Im always receive this message

"Login not available
Facebook is currently unavailable for login, you can try logging in again, or just browse logged out for now.
HTTP Error 500 (Internal server Error)"

While I could access facebook normally using Rockmelt browser.
Please guide how to fix it.

Im using (windows 8)
Thanks