Rev 1.0 variant
F1 was shipping BIOS, F2 was released the following month the same year (2015). G4400 is supported with BIOS F2... Its probably safe to say your recently acquired board has at least F2.
Rev 1.1...
F5 was shipping and supports G4400
The 5 beep behavior for missing CPU sounds normal
For now, only test with onboard video
Disconnect power to MB
Perform a battery pull (3 min), reinsert battery
Reconnect power
If the systems runs after power up (stays running) , but video is never initialized....
Recheck all of your power connections - ensure the 12v ATX supplement at the top of the board is properly seated.
The single DIMM should be installed in DDR4_1... farthest from the CPU on right
Test using display port or HDMI to a 24in or less display. If you have another HDMI cable to test with try both. Borrow a monitor or cable if needed.