Did you get this router from your ISP or did you buy it?
What Hardware version is your router? Look at sticker under router.
What Firmware version is currently loaded? Found on routers web page under status.
What region are you located?
Default access to the routers login page is Admin and password is left blank. If they setup the PW, then you can try a factory reset of the router and this will put it back to defaults.
What ISP Service do you have? Cable or DSL?
What ISP Modem do you have? Stand Alone or built in router?
What ISP Modem make and model do you have?
If this modem has a built in router, it's best to bridge the modem. Having 2 routers on the same line can cause
Double NAT connection problems.
To tell if the modem is bridged or not, look at the routers web page, Status/Device Info/Wan Section, if there is a 192.168.0.# address in the WAN IP address field, then the modem is not bridged.