Hp Probook 440 G4 cannot boot - No M2 sata disk in BIOS

[Serafim1]

I have a Probook 440 G4 that suddenly stopped booting and either showed the 'boot device not found (F30)' message, or it tried to boot and restarted but never got passed the initial HP screen.

Pressing F2 and letting it test the drive results in the computer hanging until its turned off.

I downloaded the HP PC Hardware diagnostic 4-1 USB key from this page

https://www8.hp.com/us/en/campaigns/hpsupportassistant/pc-diags.html

and ran it without problem. All tests passed with no errors but the M2 drive still doesn't show up in BIOS

But as soon as I try to boot the computer it hangs or shows the 'boot device not found (F30)' message.

The machine has one M2 sata 256 GB disk but has room for a Hdd, so I installed one ssd  hdd and installed windows after first removing the M2 drive. That worked like a charm. Then I installed the M2 drive again and it shows up in windows Disk manager but cannot be activated, and is therefore inaccessible.

I need the data on the M2 drive and would be very grateful for any help that I could get.

Thank you

[Serafim1]

I forgot to mention that I also flashed the BIOS and have now vers 01.32 Rev.A from Feb 10, 2020

Thanx

S