The plug-in is likely working; it’s just set to Test Mode. According to the plug-in author, that message is controlled by a checkbox in the exporter and is meant to let you run through the export/upload process without actually submitting anything to Alamy.

To change it, open Lightroom’s full Export dialog and use the Alamy exporter there at least once. The plug-in includes default export presets, and you can edit or remove them using Lightroom’s normal Export dialog controls. After you do one export with the full dialog, Lightroom should remember the last-used settings, so later exports from the shortcut menu should use those updated settings.

Also, it may not appear as a Publish Service if the plug-in is designed as an Export plug-in rather than a Publish plug-in.

The trial/free version should still be functional for testing, but it may limit how many images it processes.