New WiiU Help with Wii Controller

Hi everyone, I just bought a WiiU (used) and so far it’s been working fine. However, I can’t get Wii controllers to hook up. I’ve tried an original controller and a “knock off” brand. I think it’s the bar. But I’ve tried the one that came with it and the one for my normal Wii and both aren’t working? If it’s the port is that fixable and if so what kind of store what do that?