I have the same problem, the debug console output is as follows:
U-Boot SPL 2022.07-armbian (Jun 06 2023 - 04:52:59 +0000)
DRAM: 1024 MiB
Trying to boot from MMC2
MMC Device 1 not found
spl: could not find mmc device 1. error: -19
SPL: failed to boot from all boot devices
### ERROR ### Please RESET the board ###
This looks like a problem that has occurred in the past, the cause may be related to the eMMC driver in u-boot, I found some links:
https://community.ipfire.org/t/friendlyarm-nanopi-r1-flash-image-to-emmc/594/5
https://wiki.ipfire.org/hardware/arm/friendlyelec/nanopi-r1