ROCK Pi4a doesn't booting

Hallo together,

i´m using ROCK PI4a with 64 GB eMMC - Card.
If I flashed the memory - card the system doesn’t boot. I saw, that a signal is going out to HDMI - after few seconds the POWER - LED is going out. Can everybody help me, please.

It is urgent, because I use these Computer on my “HighPerformance Cloud” - System and I must do a lot of thing, because I had a demonstration with them…

Best regards

Matthias

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