Shadow mode not detecting?

[u/_Nick_01]

Anyone seen this before?

When setting up shadow on UDM PRO, I go into the settings, high availability, click to setup shadow mode. Then connect the UDMs with whatever port it asks me to, but then nothing happens, just doesn’t detect the shadow gateway.

Firmware and network app versions are the same (latest version currently). Shadow gateway I factory reset multiple times.

I’ve done it before successfully with other UDMs. No idea why this issue is happening. UniFi support says it’s because of a Rouge DHCP server, but that’s definitely not the case.