Ubuntu 21.04 on SSD through PCIe card

I installed a new Samsung 970Pro ssd on the motherboard through a PCIe card. It was shown in Nautilus and I can write to it.

Then I installed Ub on it. No problem at all. But the desktop in not showing the new SSD in the uefi/bios and refuses the start up from th ssd. The board is an ASUS P8H67-M PRO motherboard.

Is there a solution.
thanks in advance