Boot laptop?

My laptop went normally today all day earlier wanted to go back to my laptop but then came no bootable device

Insert boot disk

then googled and saw a video why that would be so then you should go to HDDO to see if the hard drive is still there but nothing was there even though I have one

here is the link which video I watched

Could you open the laptop and see if the hard drive is not completely plugged in, i.e. The cable has loosened.

At least that would be my first step if I didn't see a hard drive anymore.

Thank you, you had to blow out just briefly and put it back in.