Failing to register secondary ISE node

[Rack&Stack]

I'm running an ISE lab for practice. I am failing to register an ISE node:

When I hover over the exclamation point, it says:
Registration Failed
Sync Status: Node Registration or Sync failed. Please de-register and register the node again

On my Secondary ISE node, it still thinks it's a standalone deployment:

My devices have matching settings for:

• DNS settings
  • DNS server IP
  • Reverse and Forward lookup configured and working for both nodes
• Time
  • Time zone: America/Chicago
  • NTP server: time.nist.gov
  • Matching time when using the "show clock" command
• Software Version: 2.7.0.356
• Certificates:
  • Both devices have an internal CA cert in their trusted certificate store
  • Both devices have an internal CA signed certificate in their system certificate store that is used for admin, EAP authentication, RADIUS, DTLS, and Portal
  • Both nodes should trust each others certificates
• Network Connectivity
  • Both devices reside in the same subnet and can ping each other
  • There is no firewall between the two nodes

Is there any logs I can check to see why the registration failed?

[Rack&Stack · Accepted solution]

This has been resolved. It was related to bad network connectivity between the two ISE nodes.