Could you perhaps provide a screenshot?
It sounds like you're in a map that you don't actually have files for. It will appear as if you're standing on complete black, with nothing around you but black. If you downloaded a map recently, re-download it and replace all the files, making sure you put all files into exports.
Adding on to what's already been mentioned. If you downloaded the map, make sure that you're putting them in the exports ( or whatever files it tells you in the 'Read Me / Info' text if it is provided. Another thing to consider is making sure the files aren't corrupted or have any issues itself. The size of the map might give you some issues and your internet might not be able to handle it. Make sure to delete everything that came with the map and doing a full clean and trying again if nothing above helps. If the problem persists, it could be the map. Hope something works for you ~!