Why can't I see some planned drills in the training event?

If a user is unable to see the created drills within the training session in Planning, displaying an empty raw within the event, this means that the exercise(s) has most probably not been shared with the said user(s). To solve this, you will simply need to speak to a user with the access the the specific drills and let him/her share it with your user, from Manager - Drills - Drill's card:

Additionally, to make sure that the users see the drill inside the planned section of the training event within the Mobile apps, you need to ensure that they are also selected in the list of 'Shared With' for the different planned drills. In case they are not, and this applies both to staff and to players, they won't be able to see the shared drills in the respective calendar sessions in the mobile app.