I will leave here all I have done along with Netgate support.
First of all, I tried to read through console port if there was any data being retrieved by the firewall (https://docs.netgate.com/pfsense/en/latest/solutions/sg-1000/connect-to-console.html), but nothing was received. I have connected that console port, and then turn it on till it shutdown, but no outcome.
After this , I made a NVRAM reset used for SG-series units:
• Remove power from the system.
• Remove the case and orient the system with the Ethernet ports facing you.
• Locate the NVRAM reset jumper located just the left of the CPU heatsink.
• On early models it is labelled J8, on later models it is labelled J10. Only one of the two will have pins and the jumper present.
• Move the jumper from pins 1 & 2 to pins 2 & 3.
• Power the system on. The STATUS and SATA LEDs will light briefly then go out.
• Remove power, move the jumper back to it's original position and reattach the case.
But also no luck.
I really hope this info could help others, but one thing is for sure, I have received support from Netgate when there was 5 AM at their timezone, and we start talking through ticket support with gaps between 5 and 10 minutes. This is something I really appreciate, not leaving consumers to their luck, in very hard situations. Note that I didnt had a support contract, and start that ticket as a pfsense user with acommunity edition! And thats why I will buy again Netgate, in this case two XG-7100 units for high availability even being difficult to buy such devices here in Portugal.
Netgate ♥