Do you have secure boot on, in the bios ?

Have you considered a different linux distribution ?

Thanks for the reply, yup secure boot is enabled - exact settings followed please see link below

https://dellwindowsreinstallationguide.com/mint-20-1/ 

The thought did cross my mind to try another distro Zorin, but I think being Ubuntu based also uses the same Ubiquity installer, another one under consideration is MX which is deb based, might be an option.

Just tried starting up machine this morning, within a few hours it reverts back to not being able to detect NVMe drive.

Under the Boot sequence there is only one option (Ubuntu), whereas before I used to see the NVMe drive, is this correct?

Thanks

Yup, in the beginning tried every combo of BIOS setting, the main problem I had each time is getting back in to reset or try another configuration, not sure what is happening overnight but it loses sight of the NVMe drive.

When it was running Windows in RAID mode no such problem, this might be an indicator that NVMe on a non RAID setup (i.e AHCI) is a no go.

Forgot to mention replaced CMOS battery as that looked good as a the culprit as did a poorly earthed extension lead.

Reading various boards it appears to be a fairly common problem, Dell acknowledged the issue here https://www.dell.com/support/kbdoc/en-us/000177843/precision-towers-3420-3620-system-hanging-at-the-dell-splash-screen-or-failing-to-post this is my exact model too, BIOS upgraded to Precision_Tower_3620_2.19.0

What I may do is get another PC to experiment with, the hardware connections are getting a little fatigued taking in and out which may lead to poor connectivity in itself. I'll give SolydXK a go when I do.

Cheers

Have you tried turning "off" secure boot ?

"Under the Boot sequence there is only one option (Ubuntu), whereas before I used to see the NVMe drive, is this correct?"  >> not sure tbh.

Try this one https://solydxk.com/

Well, the nvme in non raid mode being not ok is not factual. I boot from a nvme in the flexbay, and the setting is ahci.

But windows ( on a 5/7820 ) requires an intel enterprise driver to see the nvme at all. I'm not sure if the same goes for the 3620

I will check next time I need to reboot ( by memory I think I saw both things in different times )

The button on the back is a self test for the psu. It's not supposed to be used unless to test the psu, and keeping it pressed for too long "may" not be ideal ( got that impression from some older posts ).

Are you still under warranty ? ( aka, did you try prosupport to see , if under warranty, if they have some notes for this kind of situation )

ahh okay, when you go into your BIOS and look at boot sequence does it just show the OS, in my case Ubuntu or does it show the drive itself ?

When I pop a DVD or USB in it will search for these adding them into the boot sequence, the fact the NVMe drive is not there is a concern.

btw, the power switch at the back, any ideas what the function is as it seems to bypass the 'quick power on' eventually getting it to start.

Thanks, Dell have contacted me when I registered but this machine is just out of warranty, that said not sure it would be covered as removed original OS.

For the moment going to switch back to Win 10 using the Dell restore tool, will let you know if problem persists afterwards.

PS, even replying here I get stuck lol, this captha thing is a pain

The captcha is random, sometimes I get it too ( no clue what's the trigger )

Sounds like a hardware problem. 

I would troubleshoot in this order.

- Power Switch
- Power Supply (or harness/cabling)
- Motherboard (or something on it).

I had a little machine that was working fine. Started doing this after adding some extra ram dimms. Troubleshooting revealed the power-supply had gone weak, and those extra DIMMs used just a bit too much power (to always start and Post).