eMMC not recognized by U-Boot on Alta

The eMMC works in the operating system when I boot from the SD card.

However, if only the eMMC is installed, U-Boot is not able to read it.

From the UART screen

Scanning for bootflows in all bootdevs
Seq  Method       State   Uclass    Part  Name                      Filename
---  -----------  ------  --------  ----  ------------------------  ----------------
Scanning global bootmeth 'efi_mgr':
Card did not respond to voltage select! : -110
unable to select a mode: -5
Cannot persist EFI variables without system partition
Scanning bootdev 'mmc@ffe07000.bootdev':
unable to select a mode: -5
unable to select a mode: -5
unable to select a mode: -5
unable to select a mode: -5
Scanning bootdev 'mmc@ffe05000.bootdev':
Card did not respond to voltage select! : -110

U-Boot version

=> version
U-Boot 2025.07+ (Sep 04 2025 - 17:43:40 -0400) Libre Computer AML-A311D-CC Alta

aarch64-elf-gcc (Linaro GCC 7.5-2019.12) 7.5.0
GNU ld (Linaro_Binutils-2019.12) 2.28.2.20170706

Can you provide the output of the following on the u-boot console:

mmc dev 0
mmc dev 1
=> mmc dev 0
unable to select a mode: -5
=> mmc dev 1
switch to partitions #0, OK
mmc1 is current device

Can you provide photos of the board connector and the eMMC module?

What would cause the eMMC not to work in U-Boot, but work fine in Linux?

Is Linux using HS200 and U-Boot is trying to use another mode?

Or is it because Linux is using 8 data lines for the eMMC, while U-Boot is using 4 data lines for eMMC and the other 4 data lines for the SPI NOR?

Not sure about the default in the u-boot driver but it could potentially be 8 lines in u-boot and 4 in Linux. Please have them ship you another module.