you can also try the last 8 of the serial number. If that doesn’t work, you might have already changed the login info. If you did, you can try factory resetting and reinstall (write down what you change the password to) it. 

I did what you suggested and it does not work. and I have never changed anything. 

could you let me know how to reset factory settings? 

Hi  dejavu444,

Here are the steps to complete the factory reset:

You can find a tiny hole on the back panel of the modem.

Please disconnect the coaxial cable and insert a paperclip into the tiny hole (the reset button) and hold it for 35 seconds.

Then reconnect the coaxial cable, and once the modem fully reboots, connect any of the devices to the default Wi-Fi network and access the web manager page.

Hope this helps! 

Hello Priya, 

I did it, however, it did not work. 

Did you try using the default credentials on the webinterface? Username is admin (all lowercase) password is password (all lowercase. May I know what is the error message you're getting?

Try different browsers and/or pc. Also make sure any password managers have been disabled. I’ve seen them overwrite passwords

Please try using the password as “motorola” all in lowercase