Hello abhishekbafna

                                   We understand that you are unable to access modem interface or GUI and the surfboard central app, in this case we would suggest you to try uninstalling app and reinstall it on  different device or on the same device then try logging in if still you same issue persist you need to perform hard reset on the modem to get the modem configured then it will allow you to login to the surfboard central app.

                                     But after resetting the modem will go to default setup any custom settings will be removed so use the default network name and password to connect to your network.

Let us know if this helps