I'm not getting any logs after a flight.

I'm running version 1.4.17, and I have 'log to file; checked and it says 'log all packets to /sdcard/andropilot. When I open andropilot it comes up with a message saying 'usb link logging'. I have a 3dr radio directly connected.

Previously I only had internal memory on my tablet, and under internal memory/andropilot there are the folders newlogs and uploaded. A couple of weeks ago I managed to find a log in the newlogs folder, but have had nothing in there since. 

Today I tried putting an SD card in, so that the path /sdcard/andropilot would exist, but after opening andropilot and connecting to the APM, there are no folders or files created on the sdcard.

Help please!