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

If a user is unable to see the created drills from within the training session in Planning, this means that the drill(s) has most probably not been shared with the said user(s). To solve this, you will simply have to navigate to Manager > Drills, and within the desired drill, make sure that the users are included in the list of 'Shared With'. 

Additionally, to make sure that the users see the drill inside the planned section of the training event (within the Webapp and 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.