Dell OptiPlex 7440 All-In-One Owner's Manual 

How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Computers 

If black screen persists:  How to Recover the BIOS on a Dell Computer or Tablet 

Also, are you sure the PC is getting power?

When no post, you need to open it up and remove hdd and ram, remove all external usb devices connected then reinstall only one ram, test post again. try this for each ram.  If still no video, proceed to replace cmos battery w a new cr2032, then clear cmos settings by motherboard cmos jumper.  Use the manual given by brad to look for jumper and battery location.  The jumper (#8) is on the right side of battery (#5).

Yes, the pc is getting power.  We'll try redx's response tomorrow. 

I tried setting the cmos jumper on the "CMOS jumper option" from the Password jumper and the pc will not power up when trying to reset the cmos settings.  The hard drive has to be removed as well?  I don't think I've ever had to remove a hard drive to reset the cmos settings.  

The warranty expired in 2021.  2016-2021.

I suppose your 7440 isn't under warranty yet?  Not too unusual for a monitor to die on any AIO.  1 or 2 little fans to cool everything.

You're right; removing HDD doesn't reset CMOS/BIOS.  The point of it is with HDD removed, when you turn it on, it should give you an error message.  If not, then it's not the HDD that's in error.

When I've troubleshooted RAM, I did it with HDD installed.  That way, if it's not the RAM in error, I don't get an error message.

I did plug in an external monitor using display port and the hard drive did boot to the Windows 10 login screen connecting to our domain but now its not booting up.  I'll shut it off for awhile.  

The solution did not work.  I just pulled the hard drive out and found another Optiplex 7440 aio and got the user another workstation.  Thanks.