In normal operation there are two configuration copies in a RAID controller/array system. One on the controller and one on the disks. Obviously the configuration, both of them, in your instance have been lost. I can't say why, but without a configuration found that seems to be the case.
If you previously saved your raid configuration to a file, you could restore the configuration from that. If you don't have a configuration file, you could try recreating the RAID 5 with THE EXACT same parameters, and NOT DO an initialization. If you do an initialization, all data on the disks will be lost. That may be able to recover the configuration/array.
Beyond that, you would have to restore from your backup.