I can't login to router

Hi,

I've tried to log in to the router by 192.168.1.254 as it says in CMD ipcofig. I get the log in window but whatever combination of login/password I use I can't log in. admin/1234 doesn't work.

I’ve tried to reset the device still no luck. This is important as I can't change the wi-fi password.
I’m connected to P-2812HNU-F1 vT

Thanks in advance for your help.