I too have this same product. I tried a couple of known-to-work-great-in-Raspberry-Pi-4 MicroSD cards (Sandisk Ultra, Sandisk Extreme Pro), and both failed to boot. I installed Raspberry Pi OS 32bit Bullseye in one, and Raspberry Pi OS 32bit Buster in the other.
In both cases, at boot time, the OpenWRT which is in the 32GB eMMC of the CM4 gets booted up. The MicroSD cards are ignored.
Is there a way to indicate or cause the CM4 to boot from the MicroSD card, and ignore/bypass the eMMC?