If something is rattling and the unit does not power up, then there is definitively an internal fault.
If there is no power at all, no lights or sign of life, then it is likely the power cord attachment to PSU board , or faulty PSU board. The rattling noise in that case can only be heard if shaking the unit, and it is cause by a part that detached from internal circuit. The part probably caused a short and consequential PSU failure.
More commonly the unit will be powering up, and you hear noise from the internal DVD drive. In that case there is either a disk stuck inside the player, or there is a mechanical failure concerning the DVD drive.
If there is a disk stuck inside the DVD, try ejecting the disk, follow instructions detailed here:DVD player system won't...
Either than that,any other internal fault that makes rattling noise can only be repaired disassembling the unit.
If the rattling noise is coming from the DVD drive, and there is no disk inside, then the DVD drive must get replaced.
If the unit is less than one year old, call the number listed on user guide to get it repaired.
If the unit is not under warranty cover anymore, the repair may result more expensive than getting a new Alba or similar brand player.