When adding apps to the NotifyMDM Mobile Apps list, the Apple App Store URL you provide may not be accessible to all users if some users accessing the list are located in different countries. 

Apple currently maintains an App Store in Australia, Canada, France, Germany, Italy, Japan, New Zealand, Spain, the United Kingdom, and the United States.

To accommodate users in various regions, you may have to add the App to the list more than once, using unique URLs associated with the App Store in regions where your users are located.  Make sure you also supply App names that include the country or region so that users can select the correct app from the Mobile App list that comes down to their device.

For example, add this app twice to accommodate users in both the US and Great Britain:
Using this URL for FileMaker Go users in the UK:
http://itunes.apple.com/gb/app/filemaker-go/id379686220?mt=8&ign-mpt=uo%3D4
Using this URL for FileMaker Go users in the US:
http://itunes.apple.com/us/app/filemaker-go/id379686220?mt=8

Another option is to create separate Policy Suites for users in each country or region. 
Users in various regions can also be grouped by creating separate Organizations.
Creating separate policy suites or organizations will allow you provide mobile app lists that include only the apps relevant to users in a particular country.