Missing or Select Proper Boot Device Error

Power on the PC whilst tapping the Del key to enter the APTIO BIOS Screen 

Use the Curser Keys to navigate & the Enter Key to select 

From the main screen, select Boot

Boot option 1 should be Windows Boot Manager (which is on the SSD, or NVMe)

Or the name of the SSD/NVMe  

Make sure you have "Windows Boot Manager" or "the name of the "SSD" or "NVMe" always set as Boot Option 1.

If Boot Option 1 is set to a different device, for example the larger mechanical HDD.

Select/highlight  Boot Option 1 press enter

Change Boot Option 1 to "Windows Boot Manager" or the name of SSD or NVMe in the drop down menu screen

Next go into Hard Drive BBS Priorities

Similarly set the name of the  SSD or NVMe as Boot Option 1

Press F10 to save and exit, and press Y or enter to confirm.

Windows 10 should now  boot normally

If the above steps didn't resolve the issue. Please go into the above screens and take some pictures to send to us.