Cannot register a cluster, other causes
If you cannot register a cluster with DPS and none of the errors mentioned above are the cause, the following might apply.
The Knox hostname is not reachable from the DPS host.
The user who is logged in does not have Admin role in Ambari.
Verify that the hostname where Knox is running is valid and reachable from the DPS host machine. If it is reachable, try adding the hostname resolution to the DPS container using the ./dpdeploy.sh utils add-host <ip> <host> command.
Verify that network connectivity settings, such as firewalls, are correctly configured.
Verify that the username is an Ambari Admin on the cluster. If not, make the user an Ambari Admin user, by logging into Ambari, selecting the user, and providing Admin privileges.
See the DPS Support Matrices for supported configurations.