x86 MotherBoard Bring up

[firasgany7]

For those who has experience with Intel x86 motherboard design and bring up.
I'm in the middle of motherboard bring-up that has Intel Tiger Lake UP3 CPU.
Seems like I had a good run so far at power-up sequence.
please check my reddit post that to see the images since I couldn't upload them here: https://www.dropbox.com/s/va7odkfqnmdyyqx/SBC-TI22_1_0.pdf?dl=0

as you see, I still can't get SLP_S5# = High, which means I'm still at the sleep state.
Note 1: power-up sequence is controlled by an FPGA.
Note 2: SLP_S0# is connected to 100K PU according to INTEL Platform Design Guide, as opposed to INTEL Validation board that has 100K pull down.
I pulled SLP_S0# low from FPGA (now it’s on ~500mv voltage). This change Still didn’t get me to SLP_S5# = HIGH.
Note 3: I flashed BIOS Binary to BIOS-SPI FLASH AND seems like the SoC is trying to communicate with  the SPI Flash but the SoC is not proceeding to higher states.

here is a schematic for my motherboard for those who have Dropbox account:
https://www.dropbox.com/s/va7odkfqnmdyyqx/SBC-TI22_1_0.pdf?dl=0
I would like to get some debug ideas that could help checking the source of the problem