This article presents what should we check first if Channel 5 & 6 of DSA E2800 are showing as disconnected:
Verify if the expansion slots are connected correctly (page 21)
Afterwards, wait a few minutes until they load up, and only then start the DSA S2800.
Now, you can check in the Configuration Manager to see if the IP addresses need to be changed.
Once you verify that they are correct, you can add the Device in Configuration Client.
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