Hi Michal,
Are you using LPU-1 or LPU-2? Only the LPU-2 has support for network control and feedback. It also has a webinterface, including a monitor page. You can see any commands that are send and received there.
For OSC the /pb01/ac should work, as long as all the network settings are setup correctly. (check the incoming port on Kiosc)
After saving the showfile to Kiosc, make sure that you are not running KioscEditor when testing feedback, especially not on the same machine as Kiosc. Close everything, then open Kiosc. Then make sure you send an API command to the LPU using Kiosc. (You can send the "hello" command) so the LPU knows where to send the feedback. Now start a playback that was previously not active, and the indicator should light up. (As previously mentioned, look at the monitor page of the LPU-2 to see if and what it sends)
For UDP, it is pretty much the same. Do note that the commands are a bit different though, it would be "pb01/ac" instead of "/pb01/ac"
Greetings,
Bootsy