I just wanted to add for the guidance of other people replying that the 128 MB and 512 gb versions of the Transcend MTS600 has been reported by users to be compatible with your NUC model, so it is unlikely that the drive is responsible for the start-up problem.
Like with televisions, the NUC uses blink patterns of the LED to help diagnose what the problem may be. I recommend observing the blinks of your LED and comparing them to the blink codes on this sheet.
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Thank you very much to MartyG for the suggestions posted above.
The problem could be related to the memory RAM, so besides checking the blink pattern we can also test the NUC with just one stick at the time with both sticks, this is just to rule out a possible problem with one of the sticks.
Also, we can test the NUC without the SSD, we should get the BIOS or a boot agent error, and by doing this w can rule out a possible problem with it.
On the following link you will see the system memory for the NUC, if you check your memory sticks you will see they have a part number, if it is not showing on that list, then please let us know that number so we can check the specifications of it to make sure it is fully compatible:
The NUC worked fine before or it never worked?
Please let me know the results of trying the steps above.
Any further questions, please let me know.