Even when your board is end of interactive support (Intel no longer provides email, chat or phone support for this product), we will try to help you as much as we can with your situation.
In order to better understand your issue, could you please provide us with the following details?
Are you using a USB Flash drive or an Internal DVD-ROM?
If you are using a flash drive then please try by re-formatting it and make it bootable again
Now if you are using an internal DVD - ROM can you please try with and external usb DVD- ROM?
Following up on this matter, is there any particular reason why you want to use the Intel Deployment Assistant?
Perhaps you can try a normal installation without using the Intel Deployment Assistant and see if you are able to access the boot device this way.