N300 wifi range extender bought used

Hello all, I bought a used N300 WiFi range Extender Model EX2700 from Amazon and am having trouble using it since it has been previously registered. I've never really done much with devices like this, but desperatley need this to do my online classes this semester in my room which is relatively far from my router. I tried registering the serial number, but since it's previously registered it will not let me move forward. I'm sort of in a rut now wondering where to go and figured I'd be able to ask here since the manual is only for setting up a new device. I have no information from the previous user so I'm really hoping this isn't a bust, but I understand if there's really nothing I can do. Thank you.