Need technical support

I have a Kentaur day/night vision monocular. It is fairly new as I had bought it only last year. I had picked it up one day to use it and the night vision scope no longer works, only black is visible through the eyepiece. I know it is not the batteries as I have put in fresh batteries, and the IR illuminator seems to be working fine. I have taken very good care of this device and have not exposed the night vision scope to any bright light. The night vision mode just simply stopped functioning. I had contacted the manufacturer of this product, but they no longer have any more of these kentaur day/night vision monoculars, or repair parts as they have discontinued this product. Can you think what the problem could be and how I could repair this myself, or where I can have it repaired?

Thanks,
Cannon