AB350M Pro4 w/ Ryzen 2200G - No POST, Boot Loop

If you have access to another RAM module of a different model/brand you can give that a shot too. While Ryzen has improved a lot regarding RAM compatibility it's still far from perfect. In fact, the vast majority of failed POST situations on a new build are still turning out to be RAM compatibility related. 

As for the BIOS update and compatibility stated on the box, my contacts at ASRock informed me that there are 2 types of compatible board, the first are new boards that are flashed with the latest BIOS during manufacture and the second are existing stock that were flashed by hand in preparation for Ryzen 2xxx. According to my sources, you can tell the difference by the fact that the new ones will have a sticker on the BIOS displaying a compatible BIOS version where the ones flashed by hand simply have a sticker applied to the box "Ryzen 2000 Ready" as you noted, while the BIOS sticker remains that of the original manufacture version. 

Your board appears to be of the hand flashed variety. This is a good thing because the board has been checked twice. 

It is always possible that a board can slip through the cracks somehow but from what I have been told, by trusted sources, it is highly unlikely. Typically, when there is an issue with a board it occurred though rough handling, these boards go through a lot before they hit store shelves. 

Also be sure to leave the system powered on for about 20 mins, sometimes it can take a while before the RAM boot training allows post. We have frequently seen no POST issues that were simply the user turning off the system too soon.

Regardless of what the issue turns out to be, we are here to help :)

Put battery back.  Reinstalled RAM.  Powered on, and let 30sec boot loop persist for the past 25 minutes....still no change in behavior.  No video/POST, no beep codes.

Any other suggestions before I RMA this and switch to a Gigabyte board?

As I said, RAM is all too often behind post failures with Ryzen. If the RAM is on the QVL and known to work with Ryzen then we need to look at other culprits. RMA is all well and good but if you return the wrong part only to have the problem continue it just adds to the frustration 

Our concern here is getting you up and running.

25mins and no POST is clear evidence that the issue isn't RAM training. This means either the RAM is completely incompatible or that there is another issue causing the boot loop. 

Make sure your PSU 24 and 8pin connectors are properly connected and that it is the 8pin CPU power connected not a PCIe 8pin. With issues like yours it's always best to go through the build process step by step and double check everything. While doing so be sure to use only 1 stick of RAM (test in each slot), no peripherals connected other than a keyboard and display and no SATA/M.2 etc devices connected. Try your GPU in multiple PCIe slots. Take it slow and methodical, rule out one thing at a time. If you have another system you can check individual components that are compatible (GPU, PSU etc).

If you are not already doing so, test the board outside the system to rule out potential shorts under the board (misplaced standoff, errant screws etc).

The boot cycling symptom is why I suspect the board isn't the issue. If the board is DOA or has the wrong BIOS installed then you typically don't get a loop, it usually either powers on and fans spin with no display output or, won't power on at all/ powers on then off again. A loop means that something in the POST process, prior to display initialization, is failing and the system is trying to recover, hence the loop. With Ryzen this is most often the RAM as without it you cannot get POST or UEFI, the entire system is reliant on it. 

Try to keep calm and level while troubleshooting. It is so easy to get angry with things like this  Anger clouds judgement and makes you miss things so if you feel overly wound, take a break and come back to it with a clear head. I find in situations like yours that simply reminding myself that everything is new and under warranty helps cool me off so I can focus on finding what needs to be done. 

Post back your results and good luck 

With Ryzen, history has taught me to always suspect RAM. If RMAing the board is less of an ordeal than finding more RAM to test for you then go for it.

Let us know how it goes and good luck 

That said, yes, I think it probably all comes down to specific BIOS versions.  Until I can get things up and running, I've no idea what I'm working with.  4.5 may not have the same memory compatibility as 4.7 or 4.82.  *shrug*

Sadly, it's easier and cheaper to replace the board with one that accepts the components I have, versus playing the slots (heh) trying to find memory this board likes enough.

(Currently, I'm returning the board to NewEgg as defective, and replacing it with the same model.  But if this continues, yeah, I'm gonna have to jump ship to Gigabyte or MSI.)

And then there's the boot loop.  Which throws a little bit of doubt on the memory as a culprit.

Because -- and correct me if I'm wrong -- especially with no memory, wouldn't the system simply hang at boot, trying to throw a beep code (assuming they're enabled by default), as opposed to rebooting?