BEFW11S4 (v4) Authorization

i”m currently running a Linksys BEFW11S4 (Version4) router to link 5 PCs to the internet. decently I’ve been encountering a box asking my for a under name and password. It doesn’t matter what I enter, it won’t let me in. When I cancel out, I get a red “401 Authorization Required” page.

Does anyone have any ideas? True, I probably need to update but for now I just want to figure this out.

Thanks