Error contacting server

Hi anyone, I am an older user and not very technical but I will try to explain my problem. I have a MXQ PRO box which was running 16.1 but freezing constantly. I saw a message that I should be using 17.3 and so I have installed it with no problems but of course it is an empty shell. All my efforts to install repos are met with the same error message, Cannot contact server, but on checking on the network information all looks fine. can anyone help me I am climbing the wall over this. Regards