Make sure you entered the correct password. Follow small or capital letters.
Check WLAN card installation, WLAN internet connection and browser settings.
Make sure the username or phone number you entered is accurate, as only Mobitel GSM network numbers are valid. Also check whether you entered your call number as well (031, 041, 051).
Password received via SMS is only valid for 5 minutes. After this time has expired, you have to login again, as the system does not automatically send you a new password.