I should add one clarification. When I received the 2nd STM32F7508-DK, I tried it out on the original (and only existing Keil IDE/PC at the time) and the new board did get programmed.... but then I couldn't reprogram it with another version of code, so I developed my second IDE/PC and I could not reprogram the board there. Maybe the act of programming the new board on my first IDE/PC setup damaged the board, but there is no evidence on the PCB.
At your suggestion, I downloaded the Link007 and tried to set the link to the newest standards. As you can see in the first two pictures in the attached Word file, the process worked. When I once again loaded the Keil IDE and pressed Load, the process failed as seen in the last 3 pictures of the Word file. I then decreased the ST_LINK COM frequency from 10 to 2 MHz.
I should also say that on the first IDE/PC system, in desperation I tried to use the STM32 Cube Programmer and got a whole series of messages while trying again and again.. e.g. DEV_TARGET_NOT_HALTED, DEV_TARGET_HELD_UNDER_RESET.
Also, didnt fit in initial description. Had this board for roughly 3 years now, been working fine for first year and a half, then was put aside since i had no use for it, and now trying to program it again, getting this error 🙂