Failed to get CPU status after 4 retries with aducm355

  I use IAR as IDE, and I have  several sensors, all controls by the the ADuCM355. I have done several tests , and some of them work correctly, but the others, after several tests gives me the following error message  : "Failed to get CPU status after 4 retries".

I try to :

1. Press and hold Reset and BOOT key simultaneously.

2. Release Reset key.

3. Finally release BOOT key.

Now try downloading the code.

but  i have the same problem .

You can help me .

Best regards .

Francesco