@SallyMacKenzie 

On your phone you could try going into the Router interface using the browser, its likely 192.168.0.1   or   192.168.1.1  whatever your IP range is.

Once there, try logging in as Admin Admin and check / change the wifi password from there

  @SallyMacKenzie 

Hi, 

If you are using iPhone go to Settings-> Wi-Fi-> Press the i icon on the right-> Press the Password after FaceID authorization you can see the password.

If you are connected with your Windows PC as well, you can go to "Network and Sharing Center" Click on your Wi-Fi connection-> Wireless Properties-> Security->Show Characters to see the saved password.

If you are using other devices, you can Google it to find out how to see the saved password.

Hope this works for you!