Problem when try to configure MGMT interface in Fortigate VMX

Hi to everybody

I´m trying to install the Fortiogate VMX on my computer, but when try to assign the IP I can´t, got the code -54, but if I put the IP from another LAN it´s possible, and of course I can´t reach it

Somebody knows what´s happening? because I couldn´t found a solution in forums or some other place

Thanks!