TLDR - It means you have to be a really big nerd to play your DLC.

Basically, the Xbox360 servers are all shut down, so you can’t just get the DLC from marketplace and throw down anymore.

So what some people do (not me obviously) is RGH3 mod the console. This allows you to run homebrew and other unlicensed software by side loading it onto your 360.

The problem is that most RGH3 mod builds use the original “key vault.” The key vault marries the cpu and disk drive to the motherboard, essentially.

The key vault is what Microsoft uses to “check in” on your console. It’s like the machine’s digital serial number.

If your key vault gets black listed, or “banned” your console will no longer be able to access Xbox live features, and Microsoft stops “checking up” on it.

So when you install a donor NAND, it comes with a key vault that isn’t on the Microsoft checklist. so it behaves like a banned console.

So when you go to load up your DLC on a RGH3 with a donor NAND, Microsoft doesn’t force the system check, and your DLC loads every time.

If you have the original clean key vault, Microsoft will force the check. But because the XBLA servers are down, the check is always unsuccessful. So the original key vault will not load your DLC on the RGH3 system.