On two projects lately I have run into the same error when trying to take a map offline. Sync and permissions are right, I can get through setting the work area extents, once I choose my extents I get the following message in a pop-up:
Map failed to download
The map '[Map Title]' failed to download with the message: Attempt to invoke virtual method 'java.lang.String java.lang.String.toLowerCase(java.util.Locale) ' on a null object reference
This has happened on two maps in the last 2-3 weeks. Any advice on moving this forward would be appreciated.