Can't enter into DFU mode.

I have an iPad 4 that is "disabled". It needs to be restored via DFU... for this device that is a absolute.

When I started working with it, it acted like the home button was not working and i noticed the FPC connector for the home button flex was broken, so it has been replaced.

However, when I attempt to go into forced DFU mode to start the restore, holding down the home button & wake, then release wake, the device does not go into DFU. During the first part of the DFU process (home button and wake button depressed), the Apple logo appears, then goes away, then within 1/2 second comes back and then goes away after the 10 second point. At the 10 second point I would release the wake button, but no matter how long you hold the home button, DFU does not engage.

The wake button appears to work normally and allows me to force the device to sleep by holding down for 10 seconds then waiting for the spinning wheel till off. In the state with "ipad is disabled" if is put to sleep with the wake button, it sleeps and the home button can wake it.

Trying the alternate DFU with home button depressed while inserting USB also does not get to DFU.

I have tried a new home button flex and it behaves the same as the flex on the unit. Double/tripple checked the Home Flex FPC and all runs look clean and well connected.

The other odd feature is... in any state. iTunes or the Mac does not recognize the device is present. System status on Mac USB does not recognize the device in any state (yes, it is working correctly, if I plug in my phone, the Mac sees it in the USB report line of the system report) .

Of all of this the observation of the Apple logo flashing off at 5 seconds into the DFU process... that I have never seen on any of my other devices.

Looking for any advice. Please try to limit comments to addressing the issue. I have already tried multiple computers and one Windows system. Also have tried Reiboot, but since computer is not seeing the iPad on the USB port it will never work. Also have tried many USB port. Always the same results.

Starting to wonder if the data cable to the Lightning port is flaky (since iPad can't be seen on the port) or simply the logic board has other issues that "iPad is disabled".