Os not found anymore

I installed qubes on the 2nd hard disk.
I booted windows 10 then.
Now qubeos disk did not boot anymore, bios show me message to insert media with os inside.
Basically the hd looks like empty.

Looks like or is?

looks like… because it is never deleted from the HD

Try to mount the LUKS container from a live USB. Then one could go trough the logs and try to find the root cause for this issue…

Or, if mounting fails and in case its a fresh install, I personally would reinstall as no user data is effected and searching for the issue requires usually (1) a lot of time and (2) also knowledge. So, sorry for being straight forward to you and please don’t get me wrong - the fact that you cannot derive if the HDD is empty or not, leads me to the impression, that you would start a Sisyphus task.

But that’s of cause only my humble opinion.

I already said that the HD is not empty. IT still have qubes but wont start

If you won’t listen to me and go the most “easy path” I already recommended based on your very limited Linux experience and knowledge → as the issue you have is after INITIAL installation and there is no meaningful data impacted, I would recommend to you to repeat the installation procedure.

If you want to repair, then I would probably start trying to mount the drive and check if cryptsetup luksOpen works. If yes, and your UEFI is fine, check grub. If grub and intiramfs are fine. As you were not able to even decrypt you storage device once as I understand based on the very limited information you provided, it could also be that during installation a cryptsetup relevant module was not properly included.

And of cause as always when troubleshooting go through your logs…