How do I fix black/gray screen issue on 2013 Mac Pro and 2013 MacBook Pro?

That message says one of Thousands of errors occurred. It is Not at all specific.

Kernel Panic Reports are stored in the Folder at:

/Library/Logs/DiagnosticReports

If you copy and paste that string into: 

Finder > Go menu > Go to Folder

it will take you to the Folder where those reports are stored.

Kernel panic reports are named with Date&Time and start or end in ‘panic’If you find one, please post as much as you can here, by using the “additional text” Icon in the reply footer (looks like a paper with writing). (Once the report devolves into incessant software-names or incessant Base-64 dumps with lots of AAAAAA lines, you are done.)

Please don’t post more about 20 lines of any other types of reports — they are interminable, and any information useful for this purpose is on the first screenful.

Apple acknowledged an issue with some of the GPUs back in the day and had a free repair program at the time (now long expired). However, I found that a lot of other GPU models were also affected, but were never acknowledged by Apple to have the issue. Just about every 2013 Mac Pro my organization had experienced GPU related Kernel Panics to one extent or another. We only actually had one which was covered by the free repair program.

We just learned to live with the GPU panics and tried to re-purpose the devices with more severe GPU panics to less critical roles.

Properly working computers do not suffer from panics caused by hardware that stops responding. Your computer is becoming flaky at best, failed at worst.

if you want to continue to use this computer, you may need to seek replacement graphics cards. There are no third-party cards available, and these parts get hot and after as long as these have typically been in use, they are becoming failure prone. Parts and repairs will be expensive.

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Readers recently had a discussion about the capabilities of the newest MacBook Air with Apple-silicon processor. They compared processor benchmarks with the typical Mac Pro 2013 model. The MacBook Air was as fast or faster.

your kernel panic 2 says that some variables indicating the health of the graphics cards were found to be in a state consistent with the graphics car being powered off, and the graphics card was not found.

your kernel panic 3 says the graphic card did not change its state to 'powered on' after 45488 Milliseconds, over 45 seconds.

your kernel panic 1 says that the Windoe=wserver process, that was supposed to check in after a while, dod not check in, so something must be wrong.

BOTH have to be working for proper operation -- one is not backup for the other if it fails.