admch is used for NA to collocated instances (on the same machine as NA is on). So for the time being you can set aside that part.
What seems to be broken is the DAS to NA communication. (Is NA to DAS fine ? For example create an instance for that NA and restart NA. If NA om restart becomes aware of the instance then NA to DAS is fine)
DAS tries to contact NA based on client-hostname property in that NA's config in DAS's domian.xml. This property is the "published" address by the NA. The das.properties in NA's config dir is used by NA to lookup DAS. And nodeagent.properties files in NA is used in configuration of jmx connector server in NA. Typically hostname in nodeagent.propeties is what you should see in client-hostname for that NA in the DAS's domain.xml
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