I recently purchased a used Huawei Optixstar HG8145X6 device from a TIME user, but I'm having trouble configuring it. When I try to enter PPPoE settings, it doesn't allow me to proceed. I contacted customer care, and they mentioned that the device's serial number is already registered to the previous owner, and it can't be used by another customer.

Is there any way to reset or reconfigure this device so it can be used as a modem+router? Any suggestions or advice would be greatly appreciated!