Hello Rainerdo, 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, since this specific model number is the list of compatible peripherals.
Can you try to roll back the BIOS one more version, to BIOS 0018? This will be only for testing.
You can also try to clear the CMOS, and check if the mSATA has a partition that is causing this behavior.
If it problem persist, please contact our customer support department for additional information on replacing your product
thanks for your suggestions, but I think I resolved the issue in the meantime:
I was about to return the NUC to the supplier, when I thought to give it another try. I diconnected both the SATA connector from the Transcend SSD and the audio connector, then I powered on again. This time the mSATA drive was recognized by the board and by the BIOS. I installed an OS and reconnected the SSD and audio and now it continued to work as it should.
I'm still on BIOS level 21.