I can not programEPM7128SQI-100-10

Hello!

We have been implementing EPM7128SQI-100-10 since 2006 in a line of our products. Unfortunately, we couldn't program the lot of them we had bought the last time. The lot is marked as W BEJ240413A VEJ2457513 303WA4Q0D. We program them "in-system" by means of MAX+Plus II and Byteblaster. We got an alert message: "Unrecognized device or socket is empty". We got it when programming 15 devices from 22 total.

What can be the reason of that mistake? Can you give me a hint?

Regards,

Aleksandr