What does it mean when it say check your PC and signal cables

[felicity16love]

My computer keeps on showing a box that say "self test- check your PC and Signal cables" how to I do that?
P.S. it will not allow me to use the computer of go pass that screen

thank you

 

[aford10]

Double check and make sure your monitor cable is plugged in securely at both ends.

 

[felicity16love]

will do thank you

 

[aford10]

You're welcome