Yeah, it works, thanks!

@Thomas Richard 

@Carl Love Clear, thank you. Actually in the worksheet there was "with(plots)": if I don't load the plots package, the command "DrawGraph(G,layout=interactive)" works. Thank you all.

Thanks, I'm not sure to competely understand your message but your suggestion works.

Both suggestions are usefull, thanks

Exactly! Thank you

The last one: Maple 2019.2

Thank you, it's quite intricate. I was thinking something easier, like "DrawGraph(G, sizevertex=20)".