Blinking blue light off death

My Cloud OS 5 My Cloud DL
1

Hello there! I’m using an old dl2100, serial number is WDBBAZ0040JBK-20

I guess it’s a Gen. 3 device, since Gen.2 ends with xxx-10
And I’m pretty sure I’m at OS5.

I tried rebooting, resetting with both methods (4 and 40sec) but the device is not responding. Blue per button is blinking in a 1 sec interval, but I can’t access it by any means. Neither my windows pc or my fritzbox router list the nas device. So I was thinking:

Is there a way to force install OS5 via USB Stick?
Is there a recovery?
or is it even possible to install another Linux on it?

Best regards, awaiting a few good hints.

3

Is there any way to verify it? This nas hasn’t earned it’s money yet and it’s like to repair instead of investing into a new device.