When I restarted my NAS system

I met the message "system corrupted - No USB flash module has been found "

So I asked to my seller and the guy took it to his company.

The problem is that the NAS storage works very well at the company.

However, if he bring it again to my lab., it doesn't work.

Do you know why it happens?

Now , i'm checkin the power line and voltage and my UPS.

Please give me an advise.