Okay I bought a 92 Chevy Blazer 4 days ago I went to go take it for inspection yesterday when they went to go hook up the old ODB 2 to the computer it keeps coming back make sure ignition is on

What is your question?

I try to hook my odb2 scanner up to the ODB plug that keeps telling me make sure air condition is on have it on the one when I'm supposed to and it comes back either cannot connect or make sure ignition is on