You would like to know why your Team Captain cannot update the players' names that are on his/her team from the Participant Control Panel.
When registering a group or team, the captain or primary registrant may not know all the names of the group members or players and has added place holders instead. According to this Help FAQ, the captain should be able to update the participants at a later date, but when they login, the option to edit the player's name is not available.
If a primary registrant does not know the names of the rest of the players, it is recommended that they leave the additional participant names blank. If left blank, the system will auto fill First Name = TBD, Last Name = "TEAM NAME No.1", "TEAM NAME No. 2" etc. the main registrant/captain can later add those pending participant details from their account.
However, in this case the primary registrant added their own place holders, therefore the system does not recognize the names as place holders and the ability to edit the names is not available to the Captain.
To fix this problem, go to People ->Participants, find the name of the placeholder and edit the first name to TBD. The Captain will now have the option to update the player's name.