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Do you have other DDR4 RAM? It is recommended to try to replace other RAM.
If it is still invalid, it is recommended to explain the situation to the service specialist of the Amazon store.

So you think RAM modules are defective? They work fine on my old server (Ryzen 7 4800H).

How to debug this?

I tested the same brand of memory as yours and it worked. There may be a hardware problem with your AMR5. It is recommended that you contact the Amazon store service specialist to deal with it.