can someone explain why my iPhone is the only device that is able to join my network on new router

Not off that limited info. 

1. what router do you have? 

2. what firmware is on it? 

3. what modem gateway is it connected to? 

4. what actual error are you getting? are devices not able to see the wifi? not able to connect to it? able to connect but get "connected, no internet"? what's actually happening?