Are you talking about an o2 homebox? The password for the user interface is chosen by the user himself during the initial setup of the o2 Homebox. Therefore it cannot be written on the back of the router unless you have written it there yourself. There is no username.

Only the Wi-Fi password  (“WPA2 Schlüssel”) and SSID are preset at the factory.

Hi! Thank you for your answer!

Indeed, I refer to a O2 Homebox 6741

The initial setup of the homebox was done by a worker from O2. I don’t think he asked me to set up any password during the internet installation.

Assuming that he asked me, and I forgot which one it was, how can I find my password, or set a new one?

Best,

Anca

Problem solved: I restarted the router by pressing a long time on the little black hole on the back of the router. Than i reconnected to the wifi, using the wifi password on the back of the router.

Next I went on this webpage http://192.168.1.1/#

and there I just went through with the steps, and set a new password for the web access to the router

You performed a reset to the factory defaults as described in the user manual. This deletes all user data like the password chosen by the user. The factory default is no password. I strongly recommend to write down the self-chosen password. 

btw: You can also access the interface of the o2 Homebox with http://o2.box instead of the IP address.