Question Gigabyte GA-AB350-GAMING 3 red cpu light on, no display after replacing CPU

[dryft01]

I decided to upgrade my CPU after a few years of use on this pc, so I updated by bios to the most recent one (F52i, but only the main bios) and replace my old cpu (r7 1700x) with a r5 5600, with the pc would turn on and turn off. However, when I try to put back my old cpu, I can turn on the pc but with no display and a red CPU light on the motherboard, all the fans are running inside, and not POSTing. I think it could be a bios issue because everything worked fine until I replaced my cpu, but the old cpu still doesn't work.

Things I have tried so far:
- moving the ram sticks around, trying one at a time, in different spots, etc.
- resetting the cmos for 10 minutes
- CLR_CMOS with a screwdriver
- reseating the CPU
- checking all the cables on the PSU, making sure they are all plugged in
- holding the power button and restart button to try to get into bios but it just shuts down my computer

I am not sure what to do anymore, anyone have any ideas what the issue could be?

CPU: AMD Ryzen 7 1700x, tried upgrading to r5 5600
Motherboard: Gigabyte GA-AB350-Gaming 3 (bios: F52i)
GPU: RX570
PSU: EVGA 550 G2

 

[dryft01]

I decided to upgrade my CPU after a few years of use on this pc, so I updated by bios to the most recent one (F52i, but only the main bios) and replace my old cpu (r7 1700x) with a r5 5600, with the pc would turn on and turn off. However, when I try to put back my old cpu, I can turn on the pc but with no display and a red CPU light on the motherboard, all the fans are running inside, and not POSTing. I think it could be a bios issue because everything worked fine until I replaced my cpu, but the old cpu still doesn't work.

Things I have tried so far:
- moving the ram sticks around, trying one at a time, in different spots, etc.
- resetting the cmos for 10 minutes
- CLR_CMOS with a screwdriver
- reseating the CPU
- checking all the cables on the PSU, making sure they are all plugged in
- holding the power button and restart button to try to get into bios but it just shuts down my computer
I feel like the issue is definitely the motherboard and the bios. I am not sure what to do anymore, anyone have any ideas what the issue could be? Should I replace the motherboard?

CPU: AMD Ryzen 7 1700x, tried upgrading to r5 5600
Motherboard: Gigabyte GA-AB350-Gaming 3 (bios: F52i)
GPU: RX570
PSU: EVGA 550 G2