Serial Monitor issue with Arduino M0 but not with Leonardo

Development Tools IDE 1.x
1

Hi
I'm working with Arduino M0 and Leonardo.
With Arduino M0 I cannot to see the Serial monitor data. If I use the same program with Leonardo, the program works. I tried to use also a different PC but i have the same issue.

Of course on IDE i selected the boards and the COMs.

Thanks in advance

Fausto