The Hue Emulation probably isn’t strictly following the Hue API and Alexa seems very sensitive to that whereas other implementations are more lenient in what they accept for the unique id.
The Hue documentation states:
Unique id of the device. The MAC address of the device with a unique endpoint id in the form: AA:BB:CC:DD:EE:FF:00:11-XX
So in the above example we can probably use “00:11-XX” to hold the id of the light rather than just the “XX” which is used now.
This is likely to need a code change to fix. Something along the lines of getHueIDPrefixFromUUID returning 17 characters from the UUID, e.g. “AA:BB:CC:DD:EE:FF” and getHueUniqueId using the 6 available characters to store the the hue id in the format of “00:11-XX”.