Problematic facebook account.

Did she register with her mobile number instead of an email address? If she is registered with her mobile number she must enter her number in the email address field. good luck!

Hey asmawahabbcs. i have no idea why this is happening. But i do knwo that my mum face this issue sometimes. Maybe you can ask your sister to log out of all the accounts and then try logging in again from the PC. ALternatively, try to change the FB password.

Strange Situation find out through mobile browser that what is your facebook account ID is. try to log in through facebook account ID instead of GMail ID. note-able that every user has Facebook account name not everyone knows that you can check it in your info. it may be like this facebook.com/sample1. after slash the name is your FB username try to log on through this one.

Does the connection to the website itself fail or just using the login box?

that's strange, have you already check the browser you used? or the computer settings itself from the computer? most of the time the browser being used when the site usually visit becomes visible when opening the browser