I have the same problem. Later I will try to reset the Salt router and to reset the wifi-extender.. maybe it works. I think, the Salt_2GHz should work with the wifi-extender. Does it work now with your router?

This is maybe because u might have an special sign in ur password like % or $ and so on. I had the same problem. You have to go log in your salt fiber account and change the password. But that is really complicated.

Did you finally manage to connect the extender to your salt fiber box?

You should check if the 2.4ghz wlan signal is on.. i have no idea if there is a 2.4ghz signal on the salt fibre box but this device only supports 2.4ghz anf not 5ghz.

Did you connect it via the app?