Hi Marc,
When you execute application standalone ( even standard app ) will not have parameter value in app parameters list. This app takes pernr_mem_id but not pernr.
You need to use FM HRTMC_SET_PERSON_DATA to set pernr mem id, then use the returned parameter to launch application. When you launch it in standard UI menus ( launchpad etc ) the pernr_mem_id parameter configured in launchpad will take care of generation. You don't need to set it up manually.
Thanks,
Chiranjeevi.