By the way, I send you here more Infos... maybe someone can help?

Beeing in Fastboot Menue I have following situation:

• enter: fastboot flashing unlock - then I have to confirm that on the phone. when I do that it gives on my terminal (Linux PC) out: fastboot flashing unlock FAILED (remote: 'Prohibit unlock operation ') fastboot: error: Command failed.
  On the Phone it shows: Failed to unlock the device! Will return to fastboot in 3s
• enter: fastboot flashing unlock - then I have to confirm that on the phone. when I deny that it gives on my terminal (Linux PC) out: fastboot flashing unlock OKAY [ 4.945s] Finished. Total time: 4.946s
  On the Phone it shows no Info
• In the Fastboot Menue I can choose:
  • Go Back
  • Reboot
  • Turn Off the Device

But I have something like two different loocking Fastboot menues:

• When I push the red butten left and volume up it enters in Recovery Mode. There I have following I can choose:
  • Boot recovery
  • enter Fastboot menue
  • normal Boot
• When I enter Fastboot menue, I come into the Fastbootmenue with the description above.
• When I do normal boot, the device begins an endless reboot cycle
• When I do boot recovery I come into an other looking Menue

Boot Recovery Menue:

• Here It shows following Info on top (which was not shown when I push the button volume up and the black butten below the volume down button): Version 12.1 (20240228) Active slot: b
• Here I have following I can choose:
  • Reboot system now
  • apply update
  • Factory reset: which I have already done hoping it would help - but did not
  • advanced
• Reboot System now means, that the device goes into an endless reboot cycle
• Apply Update: there I can choose apply from ADB. When I do that the phone shows: Now send the package you want to apply to the device with "adb sideload <filename>"... - and I can cancle too. I did not fiddle arround with that option but think this would probably help?
• When I cancle then on the phone it shows following: Install completed with status 3. Installation aborted.
• When I go to advanced I have new options:
  • Enter fastboot
  • reboot to bootloader
  • reboot to recovery
  • view recovery logs
  • power off

Second Fastboot Meue (entering from recovery Mode):

• Infos show above which are not shown when I enter in fastboot menue with the button volume up and the black button below the volume down):
  • product name - vidofnir
  • Serial Nr - the number
  • Secure boot - yes
• I can choose in that fastboot menue:
  • Reboot Systen mon
  • enter Revocery
  • reboot to bootloader
  • power off
• What I have also noticed, that in this fastboot menue ubport does recognize my phone right away.
• This is not the same, when I enter the fastboot menue via volume up button and the black button below the volume down.
• When I try to apply fastboot flashing unlock here, it does not give me on the phone the opportunity to confirm that. It gives right away out this error: fastboot flashing unlock FAILED (remote: 'Unrecognized command flashing unlock') fastboot: error: Command failed
  On the phone is now text to see.

Some more Infos:

• recovery Mode I enter with the red button left and Volume Up
  direct fastboot menue I enter with the volume up button and the black button below the volume down (on the right side)
• as I mentioned - do the both fastboot menue not act the same. The one I enter directly with the black button shows me a confirmation box on the phone when I enter fastboot flashing unlock. The one I enter over recovery mode does that not.

I hope this helps. For to know I would love just to have Installed Volla Phone OS 13 without any weired notice at startup of the phone. That would be very great.

Help would be very apreciated
Dom