Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Cleaning the connectors and reseating them was what I would have suggested - it was the right thing to do first.
Check as to whether this console is the type with a battery hatch on the rear edge or the underside. If so, your batteries may be due to be replaced... a low voltage from any contained battery might cause the symptoms of 'lockup' that your console is showing.
It's alive enough to respond to the magnetic safety key, but can't seem to do anything. So it isn't completely dead, which makes for some doubt still as to whether this is a 'dead console' problem, or a 'dead motor controller board' problem inside the machine.
To judge as to which of these the problem is, I will need to know what the model # ***** your Nordic Track machine is. (Also what might help, is whether it is an elliptical, a treadmill, or some other machine type.)
How old is the machine?
Has it been moved recently?
Have you tried turning it Off and unplugging it from the power for 6+ hours/overnight or longer? I suggest this as a thing to try, esp. if it has been stored in or used in unusually cool temperatures, or high humidity, etc.
Where does the cable for the incline control buttons go, at the other end from the console? to a motor controller board, I would guess.
IF so, that controller board may well be where the problem is.
But, what model # ***** ***** treadmill, exactly? or even approximately. I can find an assembly diagram, usually, if I have a model number for the machine.
(If you are done with this case, please rate my answer. Thanks.... glad to hear that some progress is being made toward getting it working.)