Hi,
Connect a system speaker (chassis speaker - red wire to +5V) to the motherboard header pins (see p.28 of the user manual Power LED and Speaker Header (7-pin SPK_PLED1 - see p.7, No. 17) to check for any error beeps on startup as it seems as though the motherboard may not be passing POST (Power On Self Test)
How many ram modules have been installed to make up the 16GB? If only the 2 i.e. 2 x 8GB did you insert them in the A2 & B2 slots? See p.22 for how to install the ram modules
Here’s a list of the AMI BIOS Beep Codes that can occur on POST. It is old so hopefully it is still relevant
Beep Code Descriptions
1 short beep: Memory refresh timer error.
2 short beeps: Parity error.
3 short beeps: Main memory read / write test error.
4 short beeps: System timer failure.
5 short beeps: Process error.
6 short beeps: Keyboard controller BAT test error.
7 short beeps: General exception error.
8 short beeps: Display memory error.
9 short beeps: ROM BIOS checksum error.
10 short beeps: CMOS shutdown Read/Write error.
11 short beeps: Cache Memory bad.