Important Notice for Ubiquiti Users
The release of the Unifi Controller Firmware 5.10.12 is not compatible with SOCIFI at this moment. Please DO NOT UPGRADE to this version. If the the firmware is already updated to the latest version, please rollback the firmware to the previous version to keep the SOCIFI external portal service running.
We will inform you when the necessary changes are done and when the new version of the FW is compatible.
The issue was caused by a bug on the firmware for APs in 5.10.12 and should be fixed in version 5.10.16
See https://community.ubnt.com/t5/UniFi-Updates-Blog/UniFi-Network-Controller-5-10-16-Stable-Candidate-has-been/ba-p/2674811 section bugfixes, Fix external guest portal cookies.