Pixhawk 4 I/O controler faulty?

Hello,

I have two Pixhawks 4, one of them fine because I see the following led configuration:

I/O PWR: green on
I/O B/E: blinking orange
I/O ACT: blinking blue
FMU PWR: green on
FMU B/E: off
FMU ACT: blinking blue

but for the second Pixhawk 4:

I/O PWR: green on
I/O B/E: off
I/O ACT: off
FMU PWR: green on
FMU B/E: off
FMU ACT: blinking blue

I have access with both Pixhawks using QGroundControl, all parameters reset to firmware default, and firmware updated to latest version.

In the “faulty” (the second one) Pixhawk I/O reset push-button has been tried, but no success.

Why could be the reason the I/O controller is not running?

Thanks in advance.