I have not seen a valid DAT file from my Mavic since around September. This is after several Mavic firmware updates (I am up to date at 1.04.0100) and DJI Assistant (Mac) updated to 1.1.6

DJI Assistant only sees a smattering of small DAT files that don't correspond to my flights and that don't really have any valid flight data in them. Back in September the files were large (300MB) and did show the flight functions and sensor readings.

I do get the flight logs that the RC loads into the DJI GO app. I suppose I don't really care about the DAT files (as long as nothing goes wrong) but I was wondering if other people can retrieve these files from their Mavics, or what I might be doing wrong. I've been using instructions linked here: http://www.datfile.net/DatCon/retrieveV3Dat.html. My general impression is that DJI Assistant does not (yet?) do everything it is supposed to do but I've used it to update firmware.

This thread may provide some help with your problem.