Have you tried exporting and then saving to compile it? Did you check it correctly? Because it checks the date when compiling. If the .bsp file doesn't have the compile date you started, it's possible the map is corrupted and has errors. You'd have to search for all the blocks there to make sure they're closed. If you don't do that, it won't always work when you try to compile, and you'll always have the same old, unmodified map.