Not reading DVD games & video

I have 2 identical PS2 scph-50003 one of them working flawlessly the other doesn't read and DVD video or DVD game. Reads only ps1 and ps2 CD only games. I changed the lens from one another and the working console was reading DVD while the other one didn't. I bought another lens and it was working on the one but didn't in the other. So lens isn't the problem. I also change the mechanisms. The spinning motor and eject mechanism. The working console wasn't having any problem. The faulty one same problem. No DVD reading. What else can I check?