Answer: Most likely the club manager hasn't assigned any training groups to the coach.
This is a small reminder that coaches' can see athletes only in their training groups. So, if a coach has a problem of not seeing any athletes, he/she should ask the club manager to check if he/she is assigned as a coach to any training groups. If a coach is assigned to a group, but still can't see any athletes, please check if there are any athletes in the group.
The same principle applies to coaches using the Smart Coaching function, so don't forget them. If a coach has both manager and coach rights, he/she still has to assign groups to herself/himself using the manager role.
A manager can check which groups are assigned to a coach by going to the Groups page and clicking on the group's name. The other option is to go to the Staff page and click on the name of the coach.
You can see visual instructions on how to assign coaches to groups here!