Did you check both planners for the same travel date? In any case, there are currently engineering works and this train will run again starting from 31 July. The ÖBB planner does show the train from that day.

Thanks for your reply! Yes I did check the same date, tomorrow to be precise. So I guess the interrail planner shows trains that aren't driving? 

That is possible. Especially the app does not get enough updates to be a reliable planning tool.

That's too bad but I will keep it in mind. Thanks for your help!