I am having the same issue, basically same screenshot as original poster.
5955WX
Asus Sage II WRX80 motherboard
256gb ram
3 pools (Pool 1: 8 - 18tb drives in 2 mirrored 4 drive Z1 pools, Pool 2: Mirrored apps pool, Pool 3: Plex Optane Transcoding drive)
25gbe network
Same issue, can not find the pool. I believe the boot-pool is on my Pool 3 optane drive as when upgrading the system I forgot to put the drive in and I received a similar message. After putting the drive in, everything worked fine and I was able to use the system normally. A few days later after a couple reboots, I started to receive the same message as the original poster. Initially I was able to manually import Pool 1 & 2 (3 was nowhere to be seen), but now it shows no pools at all. When I was able to import through the initramfs interface, I was still not able to boot truenas and was stuck in that interface.
My fear is that the Optane drive has somehow been wiped. I still see the drive in the MB bios however, so I know the system still sees it as intact. Any ideas here?