Here is the SATA adapter I am using ORICO M.2 PCIe M Key to 6 x SATA (Amazon link)
I only have 2 sticks of memory so I tried using just one at a time, and had the same issue.
I was messing around with it and noticed it booted if I had 3 or more drives unplugged, which I’m going to guess is because it couldn’t import the pool. After plugging all the drives back in it booted up but it says “ONLINE (Unhealthy)”. All the drives are there and seem to be working, could it be “unhealthy” because of the adapter?