Flirc has trouble with a few infrared repeaters, but users have reported that this one is very reliable and works well:
Some repeaters may slightly change the signal (Flirc is sensitive to small changes) so try re-assigning keys in the flirc software using the repeater not the remote.
I'm trying to use Flirc with a Harmony 900, with its built-in infrared repeater. I got Flirc to work just fine with the Harmony using it as a direct infrared remote (controlling a FireTV), but I want to control it behind a closed cabinet door. I read this article, and so I tried re-programming Flirc with the repeater instead of via the remote directly. But Flirc is not detecting the signals from the Harmony 900 repeater at all. I know the repeater is working because it works fine with all my other A/V components. Any ideas, or will this just not work?