Programs do not work after downloading

Dear everyone
I have Arduino Due. Until one moment everything worked properly. I do not remember if I did something wrong but then after a program is downloaded to memory there is no reaction (even simple diode does not blink). I use Mac software.
Maybe you have any such experience with Arduino and you can help me.

Best regards
Robert N.

Hey Robert,
First off, I'd suggest uploading a basic example program like Blink (File->Examples->0.1Basics->Blink). If this works, then I'd check your wiring. Be sure that any LEDs you've added are oriented correctly (longer wire is the cathode (+)), and all your pins are hooked up properly. If you're having any trouble with this, you should take another look at what's going on and post a question in the Wiring section of the forum. If that all checks out, then it's most likely a bug in your program, and should go under the Programming section of the forum (the example programs are very helpful here).
Good luck!

Hi Soup
Thank u for a reply. I have tried to upload example program (Blink). I guess that LED_BUILTIN means the diode "L" on Due board. There is no reaction and diode is constantly at the High level.
Could be any serious problem with the board? Programs are loaded positively.
Regards
Robert