I cannot access it 192.168.I.I

This is my first post, so please be kind if the post is not placed in the right location.
My home gateway / vivid wireless “4G” account is a few years old, but it seems that the speed is getting slow more often, which is quite frustrating.
Looking on the forum, it is recommended to have a look at RSSI and CINR parameters, so I tried to logon to 192.168.I.I as recommended, but got a fail -1 error when entering logon details.
I used directions from 192.168.I.I

Can you please help?

Is this at all related to freepbx?