WD NAS won't start orange power led keeps flashing

Hi, my WD NAS won’t start up. I’ve changed nothing to this device. The orange power led keeps flashing. I hear the drive spin for a short time, breaks a second, spins again. This is repeated. Please help me, I can’t access my data. I didn’t change the disks, they are original. Regards, Vincent

I found that when I remove the first drive of the NAS, the startup went good and I can access the data. When I put the first drive back in the cabin of the NAS, it won’t start up. Does this mean my first drive is broken and I need to replace it with a new one?