There are a couple of reasons why you cannot see all of the people in your account that you are expecting to see.
1. The missing account may not be linked to the account you are logged into, therefore will be separate and will need to be linked together by an administrator for you to see them in your account.
2. The missing account may have been deactivated as they are no longer a member.
As the organisation you are registered with manage their own membership, you will need to speak directly to them to resolve the matter.