If you are a map editor who can't view a map to which you have a link or reference, you are probably not included in an access list with which the map is shared.
To resolve the problem, you'll need to contact a Google Maps Engine administrator. Ask the administrator to check whether the access list for the map includes your name or a group of which you're a member. The administrator might need to check group membership using the Google Apps Control Panel.
Once the administrator fixes the problem, try the map again.