That could be BIOS settings or faulty SSD/HDD.  While diagnostics can be ran from the Boot & Diagnostics menu, no boot device can often involve a reload of OS if it isn't the BIOS settings. Also, I may have run into "No bootable device found" as part of troubleshooting lists in Dell documentation for certain PC's. [IMAGE] [IMAGE]  
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DS 07/20: No bootable device found? What is your go-to fix?