Cannot find the pool label for 'boot-pool' error after fresh install

[Nanashikun]

Hi,
I tried upgrading my old TrueNas Core 12 U8 Installation to 13 U3 today and ever since get the Cannot find the pool label for 'boot-pool' error.
I even tried a fresh upgrade and fresh installation from usb but no success.
The hardware I try installing it on is a supermicro A2SDi-4C-HLN4F mainboard with a NVme boot disc set to UEFI boot.
On TrueNas 12 this setup was running without any issues.
I have no clue what to do to get it back running and help would be appreciated.

Thanks a whole lot

Regards

Nana