I have the same problem on the PS4 - paid the money, downloaded the 1.1 MB patch that opened premium, but when I click on a new map, it takes me to the "buy premium" screen again. I click and select the individual maps (it states the price as $0 or Free as I have already paid the $50) and I put them on download.
So, this is what I have discovered, I am pretty certain it will work - go to the Battlefield 4 icon on your PS4 or XBOXOne - select it, but don't click on it to open it. A sub-menu should appear. It has 3 choices - Overview, Recent Activities, and Related items. Select "Related Items" and it will show you all the content you have put to download, but haven't started downloading. Select each map (of the premium add-on) and start downloading the maps. Once all maps are downloaded (about 20 GB), you should restart your system and give it a go. This time it should work!
