File | Angry Birds Epic Checking Expansion
Long-press the OBB file > Properties > Permissions = rw- rw- rw- (or 644).
The exact path is: Internal Storage > Android > obb > com.rovio.angrybirdsepic angry birds epic checking expansion file
The file name match exactly, for example: main.113.com.rovio.angrybirdsepic.obb (where 113 is the version code). Long-press the OBB file > Properties > Permissions
If the folder com.rovio.angrybirdsepic does not exist, create it manually. Long-press the OBB file >