Devices wont connect to Nighthawk RAX40 RX3000

I have try to connect the tv box to my router, the tv box is able to detect the wifi signal. However it won't connect to the router. I have changed the wifi setting to public without security WPA2. The tv box is able to connect to the router, when I changed it back to WPA2 security it won’t connect. In addition the tv box is able to connect via iphone hotspot. I have tried to reset the router to factory setting and it still won’t work. I wonder what is the issue with the router? Thank you.