Panasonic Home Theatre SA-BTT755 won't recognise usb hard drive

Hi, I hope someone can help me as i can't find anything on the internet or in the manual anywhere that might be able to.

I have a Panasonic Home Theatre SA-BTT755 that won't recognise any of my usb hard drives. I've tried a 1TB seagate, a 750GB Western Digital and a 4TB Seagate and the system just won't register there is any usb device plugged in. I've looked through the settings and can't find anything.

Can anyone shed some light on this problem.. Is there something i am missing?

Thanks.