There is a feature on Ubiquiti UniFi AP that can prevent the Circle device from pairing properly. This feature is known as 'Auto-Optimize Network,' and it may be enabled by default after an update to the AP firmware.
'Auto-Optimize' will need to be disabled for Circle to operate properly with this router.
- Log into your Ubiquiti admin view
- Navigate to Settings > Site > Auto-Optimize Network
- Disable Auto-Optimize Network.