So there are all the startup sounds after the system is turned on?
If the power is on and the hard disk is running
It's not a sure thing
If the system sounds are there and the system is turned on
Then you need to check the monitor cable and connector
Generally speaking, if the monitor is intact, even if it's not plugged into the graphics card, it will have a prompt to remind the user of the monitor's status, such as [Video not found], [Video not found], [Video not found], [Video not found], and [Video not found].