make sure the cable from the monitor is connected properly to the back of your computer
you probably have a vga cable or something
if there is no signal, then no signal is being communicated between monitor and computer
like i said, double check the wire, make sure its connected properly
if you have a graphics card try connecting it there instead
maybe the bios is set to the graphics card and not the motherboard
if the wire is connected properly, maybe its in the wrong place!
or you need to check the bios
when u boot the pc, theres usually a black screen for a couple seconds that has some information is white font, says its a dell pc blah blah blah
press F10 on your keyboard, or F9 or F5 to F10
its common most pcs u just need F10 to access bios(if you see the bios screen), otherwise its definetely a hardware problem(physical) not a software.
in my case i had to set the settings to PCI-E x16 because i installed a graphics card
then i could see and i had signal
maybe thats happened to you and the manufacterer or seller didnt put it in the right place who knows
assuming you have a graphics card
if you dont know what that is well i dunno man