Hello DL5SBI, I am sorry to hear that you are having this kind of problems on your NUC.
I'm not sure why your NUC is not recognizing the mSATA, however we cannot guarantee it is a compatibility issue.
Can you try to roll back the BIOS to version 0018 and then test the system again?
Also, please try using only the SSD. Do not connect the HDD. I would like you to do the troubleshooting using minimum configuration.
If the problem persists, please contact our customer support department for additional information on replacing your product
Thank you for your help. I downgraded to BIOS 0018, did not work. I tried recommended Crucial 240GB mSATA, did not work. I tested both drives externally with an mSATA to USB Adapter. Both were recognized by my Desktop without any Problems. So I returned NUC today to my dealer for replacement and hopefully can post a fix of the problem soon. Reading some of the other feeds, it looks like the NUC PCIe is very sensitive.