"Debugging and troubleshooting", "List of MyChat Client errors", "Error #0303".
 
Error

Error #0303: you have no rights for viewing user geopositions
 

Error description

You can't view the tracking history and current location of MyChat user on a map because you do not have rights.
 
Problem solution

Allow viewing GPS positions ("Profile", "View geoposition", "Geoposition (GPS)", rule 239) to a group of users where you are a member, or move a user to a rights group where this rule is enabled.