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Having the Intel® RST SATA mode selected is probably to increase the performance of the M.2 SSD. When installing these drives, it is important to have the latest BIOS update available for your system. Make sure your system is up to date. You can check the following link from your system manufacturer.
Please provide the report using the Intel® System Support Utility. Follow the steps below:
1.Download the Intel® System Support Utility and save the application to your system.
2.Open the application and click Scan to see system and device information. The Intel® System Support Utility defaults to the Summary View on the output screen following the scan. Click the menu where it says summary to change to Detailed View.
3.To save your scan, click Next and click Save. You can save the file to any accessible location on your computer.
4. Attach the report to this thread.
-Was the M.2 SSD working before?
-Try testing the M.2 SSD in another system.
I just tried some method and it turns out weird. The second ssd is a brand new and should not have issue, I also tried another older m.2 sata ssd which worked before and should still function now, but I couldn't find it in device management. My final attempt is to switch the ssds on the two m.2 slots. first boost was not successful, and second boost it got into the system. however, the new added ssd still not detected. There should not be hardware issue, Intel® System Support Utility also only detect one ssd...
Thank you for your response.
Are you able to test the new M.2 SSD in another system to make sure that it is working fine?
At this point, you can also verify that the BIOS is up to date, and update it if needed. Make sure the M.2 SSD is compatible with your system, too
Additionally, I found the Hardware Maintenance Manual where you can find compatible M.2 SSD
If possible, please attach the report.