Optiplex 990 SFF windows 11

Use Rufus to bypass system checks like CPU and TPM 2.0.

As @bradthetechnut  suggests.

Also make sure the storage device is set for GPT.

@anne_droid​ I did all those steps yet no boot device found the ssd works in every other pc I tested it in.

@bradthetechnut​

Yes I have a win11 ssd wich works in every pc however still no boot device found in the 990.

I tried reinstalling windows on another ssd in the pc things get even stranger it hangs and goes dark with no signal

Replace 990 CMOs battery w a new battery then clear CMOs settings via motherboard RTCRST jumper. Old pc cannot find good working bootable ssd is often due to corrupted cmos.  The observation of normal boot from Linux does not necessarily guarantee it would boot from Windows 11.  

If still cannot find Windows 11 ssd, go inside bios to change SATA operation to AHCI (default may be RAID).  This is often the cause of old pc not finding bootable SSD.

PS

OP need to make sure Windows 11 ssd was booting from UEFI bios on other pc.  This would confirm Win 11 was installed in UEFI environment. 

@redxps630​  Thanks for the tips. The battery was fine I did a reset. It tries to start but stops after windows logo and shows inaccessible boot device 0x7B error.

Check bios sata operation.

reset ? Clear CMOs by jumper ?

@anne_droid mentioned As @bradthetechnut suggests.  Also make sure the storage device is set for GPT.  That's nice of her.

Any way, SSD should be formatted to NTFS system and GPT file scheme before loading.  Edit:  This is if the boot drive is being reused.  I've loaded on blank new SSD's and Win10, and I imagine Win11 also, does the above automatically.

The INACCESSIBLE_BOOT_DEVICE (Stop Code 0x7B) error means Windows has lost communication with the drive containing your operating system during startup. This can happen after a BIOS setting alteration.

"Try toggling the setting to AHCI"  Likewise, if it's set to AHCI and not finding boot device, toggle from AHCI to RAID.  RAID is standard setting on many Dell PC's.

@bradthetechnut​ It was on raid I tried AHCI neither worked.

@redxps630​ No change.

May be a motherboard problem.  MB's are fairly cheap on ebay.

Please remember it's impossible to diagnose an exact cause from here.  Depending on how bad you want to keep the ol' 990 working, you might try a computer shop.

@bradthetechnut​ I see it's probably back to linux. I got it for free anyway the good part that all usb and other ports function correctly. I have had several of these older dell models give this particular issue. I had a topic about a 3rd gen i5 9010 that also did the same a lot before being resolved. The 4th gen i series still boots from win 11 ssd's without any problems.

When I mentioned replacement MB, I forgot you mentioned you had linux working.

We already know it's 8th Gen and newer CPU's that are supported.  That could be part of it.