Maverick uses Bing Map servers as the source of OS Explorer Maps (UK). Since April 2015 a license key is required to access OS maps. Maverick 2.7 Pro includes one license key but it can stop working after reaching the usage limit. It's recommended to create your own free Bing key.
1. Go to Bing and create your own Basic key: http://www.microsoft.com/maps/create-a-bing-maps-key.aspx
2. Use any name as the Application name and choose Other Public Mobile App as the type.
3. Download and open attached mapserver.txt file, or create a new text file and paste this line:
4. Replace YOUR_KEY with your Bing key.
5. Save this file to your Android device into this folder:
/Maverick/tiles/Ordnance Survey Explorer Maps (UK)/mapserver.txt