I also have this problem with DJI GO and Inspire 1.
I have CS 5.5" and 7.5", both are on 02.06.06.00 firmare and the smaller have DJI GO v3.1.50 and the big one have v3.1.38.
On the 5.5" I have white map with very small region around my home and that's not updating no matter where I go, the sattelite and hybrid are doing nothing as well.
FW 02.06.06.00, DJI GO 3.1.50
On the 7.5" I have completelly black and that's it.
FW 02.06.06.00, DJI GO 3.1.38
The map in DJI GO4 is working fine on both tablets.