Raptor Talos II no boot disk after installation

I'm looking for some assistance with installing OpenBSD 6.9 on a Raptor
Talos II system. I got the system installed, using the automatic disk
layout, but upon reboot, Petitboot doesn't see any eligible boot disk.
I can drop to shell from there and I can see the drive listed under
/dev/nvme0n1.

Doing fdisk -l /dev/nvme0n1 shows a couple of warnings: "GPT header CRC
is invalid" and "GPT array CRC is invalid". Then I see "Found valid GPT
with protective MBR; using GPT". There is some other information, but
it doesn't resemble the partition table I set up in the installation.

I am totally new to this POWER platform and I'm really lost as to where
I should even be looking for how to proceed... hoping someone here has
experience with this platform to advise.

Thanks in advance!
Alan