It looks like there is an issue with the token you are using. Did you get the integration token from the Dynatrace UI? (Settings -> Integration -> Dynatrace Modules -> Generate Token for NAM)
Also, if you have not found this already, here is some documentation on how to integrate NAM with Dynatrace:
Hopefully this helps!
Hello @Matthew G.
Yes. I generated the token for NAM and using the same for the integration token.
In the Tenant URL I am providing the following to integrate one of the cluster node: