RE: Dell Inspiron 24 all-in-one gets Black Screen when trying to turn on
Is this an Inspiron 24-5459 AIO?
I don't see any "volume" buttons on the setup diagram for the 5459. Have you tried pressing the Screen-off button which is right above the Power button? The 2 buttons above the Screen-off button are the brightness controls.
You can try powering off and unplugging the power cord from the rear of PC and from the wall. Then press/hold power button for ~30 sec. Reconnect the power cord to rear of PC and then to the wall and see what happens when you boot now...
And if this system is under warranty, you may need to contact Dell Tech Support.