Finally got the Radxa emmc (64GB) in. Applied several images (Ubuntu Server, Android TV), no boot. uSD boots fine.Image seems to write fine (many attempts). Partitions seem normal. No HDMI output at all.
Cloning a workable uSD image to the eMMC also fails to boot.
Also, uSD will not boot when eMMC is installed.
In addition I also tried installing thru the OTG port with rkdeveloptool. Image written successfully but still fails to boot.
Any suggestions? eMMC operations on RockPi4 broken?
If, in addition to the installed eMMC, I have an uSD plugged in, then my RockPi boots from the uSD and ignores the eMMC.
I wrote the images with the eMMC to uSD board offered by Radxa on the eMMC.
Yeah, Thats what I was getting at. The uSD wont boot if the eMMC is installed and it should.
I also have the same problem. eMMC just arrived today and it canāt boot.
Iāve first tried to boot the eMMC only (it had partitions and everything, just from the box marked AllNet, but didnāt managed to mount any partition) but no HDMI signal - tried few times.
Then Iāve copied uSD to eMMC and still no luck - no access via SSH, no HDMI signal.
While eMMC is inserted, uSD boots ok - no problem with that any time.
Also Iāve noticed that eMMC has two boot partitions (boot0, boot1) which are read-only and empty (only bytes NUL for the whole partitions) and other one ārpmbā which is even not readable (canāt make a copy of it). Now after uSD copy there is only the copy, two boot partitions and rpmb.
@jack can you help us with these?
One of the solutions here is to comment out everything in /etc/fstab file. That was my problem at least. System wonāt boot if there are invalid entries. You may want to mount devices later, after system boot.
This is still an issue. Still trying all of the things in the first post. Did I get a bad RockPi ?
Iām not able to boot from my 64GB eMMC, either. Heartbeat flashes on the SBC, but only a solid black HDMI monitor.
uSD boots and runs the same new Debian build, w/no probs. Used Etcher on Windows 10 to flash both.
OTG procedure will only get me into deeper do-do, so Iāll live w/uSD boot for now. Pulling the eMMC will be my last resort, having installed the heatsink w/compound and M.2 adapter.
Donāt understand why the eMMC build canāt be repaired/overwritten under the uSD OS. Someday.
eMMC can be repaired/overwritten under the uSD. Just boot using the uSD, download the image you want to write to the eMMC, uncompress it, and use:
dd if=<name of the image> of=/dev/mmcblk1 bs=1M
Shutdown, take the uSD card out and it should boot from the eMMC.
No way! Life is not that simple.
But, Iāll give it a shot 
Thanks for the tip.
Okay, first question: The download will be debian-arm64.img.gz onto the Rock Pi 4B uSD, running the same build. What tool do I use to uncompress it?
This newbie sincerely appreciates your patience.
I made a mistake in my previous post ā eMMC is mmcblk1, not mmcblk0. Make sure you follow the instructions from this one.
You have to open the terminal application. Then go to the directory where the image is (I would guess Downloads, but I might be wrong).
cd Downloads
zcat debian-arm64.img.gz | dd of=/dev/mmcblk1 bs=1M
Thatās it. zcat uncompresses the image on the fly and passes it to the dd command which saves it to the eMMC card (/dev/mmcblk1).
Shutdown, remove the uSD card, power the board.
Iāll bet that even I can follow that. (there I go, getting all cocky)
Will return to let you know the outcome. Sure would be nice to overcome this obstacle and get on with some projects.
All the best 
Iām baa-aack. At first, I couldnāt copy the image to the uSD, because of insufficient space on a 32 GB SD? Hmm. But, I managed to mount the 1 TB SSD and copy it there. But, even run as sudo:
ādd: failed to open ā/dev/mmcblk1ā: Permission deniedā
mmcblk1 is not mounted and already has 5 partitions, 2 mounted.
I forgot about permissions. 
Do:
sudo su
zcat debian-arm64.img.gz | dd of=/dev/mmcblk1 bs=1M
Or
zcat debian-arm64.img.gz | sudo dd of=/dev/mmcblk1 bs=1M
Also, it is a good idea to unmount the eMMC partitions first.
āNo passwd entry for user āzcatāā
you probably typed something like
sudo su zcat ā¦
āsudo suā has to be followed by Return, then youāll be root and type āzcat ā¦ā
Got it! Just needed āsudoā prior to both commands.
Let me try a reboot.
Bummer. Just a black monitor & SBC heartbeat.
The partitions are gone from mmcblk1. There are mmcblk1boot0 and mmcblk1boot1 disks, which are 4M & flagged RO 1. Thereās also mmcblk1rpmb disk, also 4M flagged RO 0. They were there before running zcat. Should they be there?
At this point, should I start over with fdisk?
First of all, I want to give a shout out to @lucho for holding my hand while teaching me zcat usage.
I found that, after running zcat on the image file, /dev/mmcblk1 no longer had partitions, according to lsblk. But, fdisk -l listed the partitions, but reported pmbr errors. So, fdisk -w repaired the pmbr, with a backup. The partitions re-appeared in lsblk.
But, I noticed that partition #4 was full, so I used fdisk to delete p4 & p5, then recreate them with partition # 4 being twice its original size.
Unfortunately, zcat still trashes the pmbr, so the system hangs during eMMC boot, just after the screen turns totally black, before the mouse pointer appearing.
Boot from uSD and the partitions are missing from lsblk again. And the loop goes onā¦ and the loop goes onā¦(catchy tune)
Can you try with a different image? It worked well for me with the radxa provided armbian.
You donāt give up, do you? Awesome!
Yes, Iāll download it again. This is the most recent build from Radxa and is also the current uSD source. Wanted to stick with Debian-arm64 build because it works. The Armbian_5.73.190128_Rockpi-4b_Debian_stretch_dev_4.20.0 build didnāt (last week). But stuff happens, including file corruption.
Was planning to try the same process, w/another uSD via USB adapter.
Today Iāll be shopping for counters & wood to build a workbench. So, Iāll resume troubleshooting this evening.
Very grateful for your assistance.