Thanks for your input. I tried with a different cable, different monitor and even added an external gpu just to make sure but no luck.

Have you try with different monitor, cable?

Thanks for your input. Already tried different memory modules from another working computer. I also tried memory modules from failed PC in and other computer and they are working without any problems.

A bad memory module could do that.  Remove all memory then install only one ram back in dimm slot 1.  Test each memory this way.

if possible get another ddr4 desktop ram to test pc.

Could the HDD/SSD have failed?

No problem with the ssd. It doesn't even comes to boot stage but swapped and tried in another pc just in case and ssd works without a problem.

Turn it off. Unplug power cord.  Press power button to drain flea power x 30 sec.  Replug power cord.  Power on again.

Thanks, tried that but nothing changes.

my pc and monitor has a finicky DisplayPort cable connection.  I would unplug and replug DP from pc and monitor to triple check.  There are two DP ports at back of 7060.  Users report sometimes bottom or maybe upper DP port of some new optiplex does not work.  So try both DP ports multiple times.  If still none, these ports are defective.

To verify DP cable and monitor both work, use another working desktop.  

Solid white led is supposed to mean normal.  Still no video, then the problem seems to be with onboard DP ports (motherboard).  Need to plug DP cable securely into one of the two ports before power on pc.  
when you remove all memory, it is supposed to do 3,3 amber flash for no memory detected, and not beep.
On any OptiPlex built since 2012 (that is, 7010/9010/9010 AIO), Dell has stopped using all beep codes except for the Memory Failure code. (1, 3, 2, or one beep, then three beeps, then two beeps.) If your computer was built after 2012 and is making any other beep code, contact technical support for further help.