Hello, friend!
Check whether the device model is correct. After confirmation, I cannot find the device model (B15-6766).
Generally, B series routers are home terminals. When you log in to the device web page for the first time, the device does not have a password. If you forget the password, you can touch and hold the key to reset the device. The device is a pre-configured device. Therefore, the network parameters are automatically restored after the SIM card is inserted.
If your device is customized for an ISP, you can view the login account and password on the device nameplate. You can also contact the ISP to confirm and obtain the login account and password.
Thanks!