The length of a constituent's nickname could cause the Contact Card to not display information. The Contact Card supports up to 25 characters within the Nickname field. Any constituent with a larger Nickname will cause all Relationships to disappear from view. 

This can be resolved by reducing the character length of the Nickname. This can be completed from either a Platform Manager or constituent's point of view.
(Note: Constituents will only have access to change their Nickname if access has been set up within Profile Fields. Core > Security > Profile Access > Profile Fields)
   For Platform Managers:
  1. Navigate to Core > Users
  2. Click Edit User Profile Data
  3. Search for user in question
  4. Click Edit under Personal Information 
  5. Reduce the Nickname character length
  6. Click Save & Exit
  For Constituents:
  1. Click on your name in the upper-right after logging in
  2. Select Profile
  3. Click Edit (Pencil) under General Information
  4. Reduce the Nickname character length
  5. Click Save