New router not connecting to devices

[BigT2000AD]

Hi,

I have had an engineer fit a new full fiber router this afternoon and when trying to connect my devices it is saying the password is incorrect. I had tried both the password on the back of the router and the one on the little card, for clarity, they are the same. I have reset the router using the button multiple times and it still won't accept the password given. What shall I do? As I currently have no WiFi in my house.