Look on the bottom/back of the router and post the make and model number.
Or, if it's listed, log into the router using the address and default username and password, then see if there are any settings pertaining to WiFi that need to be changed.
If all else fails, you can always reset it and try again. Sometimes, it can be as simple as powering it off for a few minutes and then back on. That's been the case for me a time or two.