Thank you for your post! Are you trying to import the maps via iTunes File Sharing? Is there enough available storage on your device to hold all of the maps you are trying to import? If you import in smaller batches of maps does it work? Does it stop when you reach one specific map? If so, if you remove that map, does it work?
If the issue persists could you please contact us here:http://help.avenzamaps.com/customer/portal/emails/new
With more information so we can investigate further?
Let me know if you have any further questions!
Avenza Systems Inc