Hmm.. How big is your database file (wms.db)? MyDocs uses FAT32 file system which means that maximum file size is ~4GB, and so if your database has reached that new map tiles won't get saved anymore (or if you don't have free space in MyDocs).

If your database file is smaller that 4GB and you have free space in MyDocs, try moving around in map in online mode (so that new tiles are downloaded) and see whether database file size increases. And also try downloading tiles from specified area with tile downloader and see whether then database file size increases.