Inspiron 5505 no bootable device after installing SupportAssist

Help! The Inspiron 5505 laptop shows "No Bootable Device" during Pre-Boot System Performance Check after I installed Dell SupportAssist. 

Background: The pc originally came with a 250 GB solid state drive and I added a 2tb new one. 

I recently reinstalled a clean Win10 on the new 2tb drive (deleted old system in the 250 GB drive) to solve the touchpad problem and installed SupportAssist thought it would be useful. Now the Bios is messed up and the pc wouldn't boot with the error. I found the only way to start the system is to enter the Bios and delete "Windows Boot Manager: \EFI\Microsoft\Boot\bootmgfw.efi" and leave "legacy: bootmgr.efi".  However, the error is back after reboot because the boot options resumed .  I cannot modify the list under "UEFI BOOT", where only 250 GB disk and USB1 are listed.  

I also tried installing another copy of Win10 in the old disk but the installation could not finish because of the error. 

Other relevant information:

  - both drives are visible in the Bios but only the old 250 GB is listed under the Boot tab

  - uninstalling SupportAssit did not help

  - disabling "SupportAssit OS Recovery" under "Advance" tab didn't help.   

  - the old disc (disk0) was set as D and the new one (disk1) was set as C. This confuses SupportAssit?

Thanks in advance!