Server powerdge r720 does not reboot the ubuntu OS (dark screen)

All worked well before stoping and restart my server via iDRAC interface (stop the system).

After that when I start,  the server refuses to load the ubuntu kernel.

When I start the server, all is going well until reaching the grub menu.

It shows me the ubuntu system line and the advancded options line.

When I choose the first one, it displays a dark screen.

When I choose the advanced options to start recovery mode, it shows

me some line and stop with error :

(sda1):  last error at time ....  ext4_mb_generate_buddy .

The thing I don't understand is that before this incident, the server did never show me the grub menu.

Also, Leds on the RJ45 interfaces (3 and 4) stop flashing when the black screen is displayed.

In the iDRAC interface, I have those errors : The NIC Integrated 1 Port 3 network link is down and The NIC Integrated 1 Port 4 network link is down.

My question is why server show me dark screen after grub menu and the NICs port 3 and 4 network links are down and how can I solve this problem?

Thank you for your help.