The MapSync service is sensitive and requires the proper files to be in the correct location for everything to work correctly. Sometimes a users file, over time, can become corrupted. Or potentially the file could corrupt on download as well. You can tell if this has occurred by the error message that is presented. It will look something similar to this image:
What you will need to do is go and delete the RemoteDB folder. This will clear out all of the map sync data that has been downloaded and remove any faulty files. You will need to go back and download the data again but there should not be an error during download this time.
If you are still experiencing issues, please submit a support ticket here:https://edxwireless.atlassian.net/servicedesk/customer/portal/2