Visit ui.com/download . Select your specific hardware model (e.g., NanoStation M5). If version 1.2.55 is not listed, it has been superseded by a newer stable version. Ubiquiti highly recommends using the latest stable release to patch security vulnerabilities.
Log into your Ubiquiti device via its IP address. Navigate to the System tab. There is often a link to "Check for Updates" or a direct download link provided within the interface that will supply the correct firmware for that specific hardware revision. upgrade firmware version 1.255 ubnt download