Stopped downloading after going to offline r mode.

Hello. I am I've setup about 8 hours of adding albums to download. I haven't found an easy way to download singles or just tracks without a Playlist even the daily foyou songs.However once I got back to wifi as I ran out of data for the month. I was stalleno downloading for about a half hour. I started adding new stuff to download yet it is just downloading the new stuff. I have not found a way to resume all the old stuff without restarting all the previously downloaded items without clearing the data and trying again.

Thanks for your assistance, 

Gregory