NetCut or Netcut-defender report you are currently running under Managed network . Which means, you are under WIFI, or your network is filter packat by MAC and only ensure registered MAC packets can go through. Good investment and indeed good work of network Administrator!!
However, what this means ?
It means all L2 packet sent out with wrong header/source are be dropped. depending on how powerful of your switch, you will notice different result from the testing. note the L2 (Layer 2) here,it means packet with wrong hardware header can still work under this network. I can give details how it work later , but for now, you just need to know you are under WIFI type network. and netCut is ready to test ARP spoof. if you are not network admin, Do not play against others please. if you are network admin, you are free to try out "CUT" now with netcut. see if it still works.