NCS Iphone Error Unknown Error (-1)

Having some issues logging on to NCS when it was previously working from the application.

The error message I am getting is NCS Iphone Error Unknown Error (-1).

I have already put in http://my.external.ip.adddress:portnumber from my iPhone and I can login with no issues. I have also removed and re-added the NCS IPhone app and reconfigured the server and it’s still not working.

any bright ideas?

Check this one first.