F2-420 bricked

[vector]

I just installed a new compatible 8GB RAM module on my f2-420
https://www.phs-memory.it/memoria-ram-8 ... 66483.html

After turning on the power, there is no beep and all hard drive lights are red.
Removing additional ram module nothing changes.
Removing HDs nothing changes, same behavior.
Reinstalled the RAM module, a beep sounds and the network light flashes on the back.
The HD status lights are red and the NAS is not reachable from PC or TNAS application.

I tried initboot usb (hopefully I downloaded the right bzImage file for my model) but didn't fix the boot error.
Since that model has no video output, it is very hard for me to understand what the real problem is and if the usb initboot is booting.
Can anyone help me solve the problem?